RESUMO
Immunoglobulin G (IgG) is one of the five antibody classes produced in mammals as part of the humoral responses accountable for protecting the organisms from infection. Its antibody heavy chain constant region is encoded by the Ig heavy-chain gamma gene (IGHG). In humans, there are four IGHG genes which encode the four subclasses, each with a specialized effector function. Although four subclasses of IgG proteins have also been reported in macaques, this does not appear to be the rule for all primates. In Platyrrhini, IgG has been stated to be encoded by a single-copy gene. To date, it remains unknown how the IGHG has expanded or contracted in the primate order; consequently, we have analyzed data from 38 primate genome sequences to identify IGHG genes and describe the evolution of IGHG genes in primate order. IGHG belongs to a multigene family that evolves by the birth-death evolutionary model in primates. Whereas Strepsirrhini and Platyrrhini have a single-copy gene, in Catarrhini, it has expanded to several paralogs in their genomes; some deleted and others pseudogenized. Furthermore, episodic positive selection may have promoted a species-specific IgG effector function. We propose that IgG evolved to reach an optimal number of copies per genome to adapt their humoral immune responses to different environmental conditions. This study has implications for biomedical trials using non-human primates.
Assuntos
Regiões Constantes de Imunoglobulina , Cadeias Pesadas de Imunoglobulinas , Animais , Regiões Constantes de Imunoglobulina/genética , Cadeias Pesadas de Imunoglobulinas/genética , Imunoglobulina G/genética , Evolução Molecular , Platirrinos , Filogenia , MamíferosRESUMO
Despite being the most abundant class of immunoglobulins in humans and playing central roles in the adaptive immune response, high-resolution structural data are still lacking for the antigen-binding region of human isotype A antibodies (IgAs). The crystal structures of a human Fab fragment of IgA1 in three different crystal forms are now reported. The three-dimensional organization is similar to those of other Fab classes, but FabA1 seems to be more rigid, being constrained by a hydrophobic core in the interface between the variable and constant domains of the heavy chain (VH-CH1) as well as by a disulfide bridge that connects the light and heavy chains, influencing the relative heavy/light-chain orientation. The crystal structure of the same antibody but with a G-isotype CH1 which is reported to display different antigen affinity has also been solved. The differential structural features reveal plausible mechanisms for constant/variable-domain long-distance effects whereby antibody class switching could alter antigen affinity.
Assuntos
Reações Antígeno-Anticorpo , Antígenos/química , Sítios de Ligação de Anticorpos , Imunoglobulina A/química , Regiões Constantes de Imunoglobulina/química , Fragmentos Fab das Imunoglobulinas/química , Serina Endopeptidases/química , Reações Antígeno-Anticorpo/fisiologia , Antígenos/fisiologia , Clostridium/enzimologia , Cristalografia por Raios X , Humanos , Imunoglobulina A/fisiologia , Regiões Constantes de Imunoglobulina/fisiologia , Fragmentos Fab das Imunoglobulinas/fisiologia , Neisseria gonorrhoeae/enzimologia , Estrutura Terciária de Proteína , Serina Endopeptidases/fisiologiaRESUMO
Murine monoclonal antibody 1A4A1 has been shown to recognize a conserved neutralizing epitope of envelope glycoprotein E2 of Venezuelan equine encephalitis virus. It is a potential candidate for development of a second generation antibody for both immunodiagnosis and immunotherapy. In order to minimize the immunogenicity of murine antibodies and to confer human immune effector functions on murine antibodies, a recombinant gene fusion was constructed. It encoded a human IgG1 heavy chain constant region and a single-chain fragment variable antibody of 1A4A1. After expression in bacteria as inclusion bodies, the recombinant antibody was purified and refolded in vitro. The recombinant soluble antibody was demonstrated to retain high antigen-binding affinity to Venezuelan equine encephalitis virus and to possess some human IgG crystallizable fragment domain functions, such as recognition by protein G and human complement C1q binding. On non-reducing and reducing gel electrophoresis analysis of proteolytic fragments of the recombinant antibody, disulfide bond formation was found in the hinge region of the antibody. From these data, it was concluded that the recombinant antibody was capable of antigen recognition, and retained several functional activities. This work forms the basis for characterization of the recombinant antibody as to efficacy in vivo.
Assuntos
Anticorpos Antivirais/genética , Anticorpos Antivirais/imunologia , Vírus da Encefalite Equina Venezuelana/imunologia , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/imunologia , Proteínas do Envelope Viral/imunologia , Animais , Anticorpos Antivirais/química , Antígenos Virais/imunologia , Complemento C1q/metabolismo , Humanos , Regiões Constantes de Imunoglobulina/genética , Imunoglobulina G/química , Imunoglobulina G/genética , Imunoglobulina G/imunologia , Região Variável de Imunoglobulina/genética , Camundongos , Proteínas do Tecido Nervoso/metabolismo , Plasmídeos , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/metabolismoRESUMO
Cold agglutinins (CAs) are IgM autoantibodies characterized by their ability to agglutinate in vitro RBC at low temperatures. These autoantibodies cause hemolytic anemia in patients with CA disease. Many diverse Ags are recognized by CAs, most frequently those belonging to the I/i system. These are oligosaccharides composed of repeated units of N:-acetyllactosamine, expressed on RBC. The three-dimensional structure of the Fab of KAU, a human monoclonal IgM CA with anti-I activity, was determined. The KAU combining site shows an extended cavity and a neighboring pocket. Residues from the hypervariable loops V(H)CDR3, V(L)CDR1, and V(L)CDR3 form the cavity, whereas the small pocket is defined essentially by residues from the hypervariable loops V(H)CDR1 and V(H)CDR2. This fact could explain the V(H)4-34 germline gene restriction among CA. The KAU combining site topography is consistent with one that binds a polysaccharide. The combining site overall dimensions are 15 A wide and 24 A long. Conservation of key binding site residues among anti-I/i CAs indicates that this is a common feature of this family of autoantibodies. We also describe the first high resolution structure of the human IgM C(H)1:C(L) domain. The structural analysis shows that the C(H)1-C(L) interface is mainly conserved during the isotype switch process from IgM to IgG1.
Assuntos
Aglutininas/química , Temperatura Baixa , Hemaglutininas/química , Fragmentos Fab das Imunoglobulinas/química , Imunoglobulina M/química , Anemia Hemolítica Autoimune/imunologia , Animais , Autoanticorpos/química , Simulação por Computador , Crioglobulinas , Cristalização , Humanos , Regiões Constantes de Imunoglobulina/química , Cadeias Pesadas de Imunoglobulinas/química , Isotipos de Imunoglobulinas/química , Cadeias Leves de Imunoglobulina/química , Região Variável de Imunoglobulina/química , Camundongos , Modelos MolecularesRESUMO
Sequences of Aotus nancymaae immunoglobulin kappa light-chain rearrangements were analyzed after reverse transcription polymerase chain reaction. Among 22 in-frame rearrangements analyzed, 12 IGKV genes belonging to the families 1, 2, or 3 were identified. Aotus counterparts for all five human IGKJ genes were found. The identity of the deduced human and Aotus amino acid sequences was between 83% and 92% for junctional regions and 74% for the constant region. Sequence comparisons between rearrangements indicated that somatic mutations, the addition of nongermline-encoded nucleotides, and exonuclease trimming contribute to the generation of diversity of Aotus immunoglobulin kappa chains. The high identity of Aotus and human IGK genes is comparable to that of T-cell receptor genes and further supports the proposal to use the Aotus Plasmodium falciparum infection model for the evaluation of malaria vaccine candidates.
Assuntos
Aotidae/genética , Regiões Constantes de Imunoglobulina/genética , Região de Junção de Imunoglobulinas/genética , Região Variável de Imunoglobulina/genética , Cadeias kappa de Imunoglobulina/genética , Sequência de Aminoácidos , Animais , Aotidae/imunologia , Sequência de Bases , DNA Complementar , Humanos , Dados de Sequência Molecular , Homologia de Sequência de Aminoácidos , Homologia de Sequência do Ácido NucleicoRESUMO
cDNAs encoding IgM heavy chain constant region (Cmu) were isolated from two metatherians (marsupials)--the Australian common brushtail possum (Trichosurus vulpecula) and the South American grey short-tailed opossum (Monodelphis domestica). Analysis of the sequences suggested that they correspond to the secreted form of Cmu in both species. The domain size and structure of the marsupial Cmu sequences were compared with other Cmu sequences and a high degree of conservation throughout vertebrate evolution was observed. Amino acid sequence comparisons revealed a marked level of sequence similarity between the two marsupial sequences (79%), relatively high similarity between the marsupials and eutherians (63%), and lower similarities between marsupials and birds (45%), marsupials and amphibians (47%), marsupials and reptiles (45%) and marsupials and fish (37%). These data allow the incorporation of metatherians into the study of mammalian IgM evolution.
Assuntos
Regiões Constantes de Imunoglobulina/genética , Imunoglobulina M/genética , Cadeias mu de Imunoglobulina/genética , Gambás/imunologia , Sequência de Aminoácidos , Animais , Austrália , Sequência de Bases , DNA Complementar , Humanos , Regiões Constantes de Imunoglobulina/classificação , Regiões Constantes de Imunoglobulina/isolamento & purificação , Imunoglobulina M/classificação , Imunoglobulina M/isolamento & purificação , Cadeias mu de Imunoglobulina/classificação , Cadeias mu de Imunoglobulina/isolamento & purificação , Dados de Sequência Molecular , Gambás/genética , América do SulRESUMO
We studied the relationship between tumour necrosis factor (TNF) and interleukin 6 (IL-6) levels, and the metastatic process in C57BL/6 mice after intravenous inoculation of B16-BL6 melanoma cells. Bioactive TNF was not detectable in the sera of inoculated mice, but these animals did show higher TNF levels following intraperitoneal challenge with lipopolysaccharide (LPS) compared to control animals. Serum IL-6 levels were increased in inoculated animals. Injection of a hybrid molecule (p55-sf2) composed of the human p55 TNF receptor extracellular domain coupled to a human constant region backbone, decreased serum TNF (after LPS challenge) and IL-6 levels in inoculated animals. Lung metastases at 7-14 days were reduced, compared to human IgG-injected control animals, but this effect was lost at day 21 postinoculation. The results suggest that the reduction in the number of metastases may be related to the effect of blocking TNF activity.
Assuntos
Antígenos CD/imunologia , Interleucina-6/sangue , Lipopolissacarídeos/farmacologia , Neoplasias Pulmonares/secundário , Melanoma Experimental/imunologia , Melanoma Experimental/secundário , Receptores do Fator de Necrose Tumoral/imunologia , Fator de Necrose Tumoral alfa/metabolismo , Animais , Humanos , Regiões Constantes de Imunoglobulina/farmacologia , Imunoglobulina G/farmacologia , Imunoterapia , Neoplasias Pulmonares/imunologia , Neoplasias Pulmonares/prevenção & controle , Masculino , Melanoma Experimental/sangue , Melanoma Experimental/patologia , Camundongos , Camundongos Endogâmicos C57BL , Receptores Tipo I de Fatores de Necrose Tumoral , Fatores de Tempo , Fator de Necrose Tumoral alfa/análise , Fator de Necrose Tumoral alfa/antagonistas & inibidoresRESUMO
Previous studies suggest a potential association between human immunoglobulin (Ig) genes and susceptibility to systemic lupus erythematosus (SLE). Ig allotypic determinants seem to confer an increased risk for the disease in various ethnic patient populations. In this study we have examined the pattern of restriction fragment length polymorphisms (RFLP) of constant region lambda (C lambda) light chain genes in a group of 78 Venezuelan patients with SLE and 70 healthy controls. The frequency of the 8-kb allele and the 8/8 genotype was significantly lower in normal Venezuelan controls as compared to healthy British Caucasians (P = 0.0002 and 0.0007 respectively). In turn, Venezuelan controls showed a higher frequency of the 18-kb allele and the 18/18 genotype (P = 0.0002 and 0.0052 respectively). However, there were no statistically significant differences in either parameter between Venezuelan SLE patients and healthy controls. Our study argues against a role for lambda light chain constant region genes in predisposition to SLE.
Assuntos
Doenças Autoimunes/genética , Genes de Imunoglobulinas , Regiões Constantes de Imunoglobulina/genética , Cadeias lambda de Imunoglobulina/genética , Lúpus Eritematoso Sistêmico/genética , Polimorfismo de Fragmento de Restrição , Doenças Autoimunes/etnologia , Doenças Autoimunes/imunologia , Genótipo , Humanos , Lúpus Eritematoso Sistêmico/etnologia , Lúpus Eritematoso Sistêmico/imunologia , Espanha/etnologia , Venezuela/epidemiologia , População Branca/genéticaRESUMO
An RNA polymerase chain reaction strategy was used to amplify and clone a cDNA segment encoding for the complete constant part of the axolotl IgY heavy (C upsilon) chain. C upsilon is 433 amino acids long and organized into four domains (C upsilon 1-C upsilon 4); each has the typical internal disulfide bond and invariant tryptophane residues. Axolotl C upsilon is most closely related to Xenopus C upsilon (40% identical amino acid residues) and C upsilon 1 shares 46.4% amino acid residues among these species. The presence of additional cysteines in C upsilon 1 and C upsilon 2 domains is consistent with an additional intradomain S-S bond similar to that suggested for Xenopus C upsilon and C chi, and for the avian C upsilon and the human C epsilon. C upsilon 4 ends with the Gly-Lys dipeptide characteristic of secreted mammalian C gamma 3, human C epsilon 4, and avian and anuran C upsilon 4, and contains the consensus [G/GT(AA)] nucleotide splice signal sequence for joining C upsilon 4 to the transmembrane region. These results are consistent with the hypothesis of an ancestral structural relationship between amphibian, avian upsilon chains, and mammalian epsilon chains. However, these molecules have different biological properties: axolotl IgY is secretory Ig, anuran and avian IgY behave like mammalian IgG, and mammalian IgE is implicated in anaphylactic reactions.
Assuntos
Regiões Constantes de Imunoglobulina/química , Cadeias Pesadas de Imunoglobulinas/química , Isotipos de Imunoglobulinas/química , Ambystoma mexicanum , Sequência de Aminoácidos , Animais , Sequência de Bases , DNA/química , Humanos , Regiões Constantes de Imunoglobulina/genética , Cadeias Pesadas de Imunoglobulinas/genética , Isotipos de Imunoglobulinas/genética , Dados de Sequência Molecular , FilogeniaRESUMO
Doze crianças de oito a 14 anos, portadoras de esquistossomose mansônica, forma hepatoesplênica, tratadas com Oxaminiquine, foram submetidas a auto-implante de cerca de 100 gramas de baço no grande omentum, em associaçÝo com esplenectomia e ligadura de veia gástrica esquerda. A esplenose foi comfirmada, em todos os casos, por cintilografia hepatoesplênica seis meses após e autoimplante. A análise sequeqncial das imunoglobulinas G(IgG), A(IGA) e M(IgM) e dos componentes 3 (C3) e 4(c4) do sistema complemento revelou:1§ antes do tratamento clínico as médias das concentraçSes séricas de IgG e IgM (4.048+-1.262mg por centoe 243 +-232mg por cento) foram significativamente mais elevadas (p<0,01) do que as da populaçäo normal. As concentraçäo média de IgG foi maior do que a de adultos na mesma fase evolutiva (p<0,05). As médias das concentraçöes séricas de IgA, C3 e C4 estiveram dentro dos limites da normalidade; 2§ - trinta dias após tratamento clínico houve reduçÝo significativa (p<0,05) e IgG (3.385+-2.182mgpor cento) As médias das concentraçöes séricas de IgA, IgM, C3 e C4 näo variaram significativamente: 3§ após segmento pós-operatório médio de 10 meses houve reduçäo ainda mais significativa (p<0,05 de IgG (2.612+- 656mgpor cento). As concentraçöes médiad de IgA (316+-68mgpor cento) se elevaram de forma significativa. A média de IgM (340+-108mg por cento) embora inferior a média pré-operatória, nÝo alcançou significaçäo estatística. Os resultados evidênciam uma imunoresposta humoral mais acentuada em crianças esquistossomóticas forma hepato-esplênica quando comparada com adulto. A imunomoduçaçäo face ao tratamento clínico inclui a diminuiçäo das respostas humoral sobretudo com queda da concentraçäo de IgG. a eplenectomia associada a esplenose acentua a queda das concentraçöes de IgG e eleva as concentraçöes de IgA e C3
Assuntos
Humanos , Masculino , Feminino , Criança , Adolescente , Complemento C4 , Proteínas do Sistema Complemento , Esquistossomose mansoni/cirurgia , Esplenectomia , Esplenose , Imunoglobulina G , Regiões Constantes de ImunoglobulinaRESUMO
cDNA clones coding for the constant region of the Mexican axolotl (Ambystoma mexicanum) mu heavy immunoglobulin chain were selected from total spleen RNA, using a cDNA polymerase chain reaction technique. The specific 5'-end primer was an oligonucleotide homologous to the JH segment of Xenopus laevis mu chain. One of the clones, JHA/3, corresponded to the complete constant region of the axolotl mu chain, consisting of a 1362-nucleotide sequence coding for a polypeptide of 454 amino acids followed in 3' direction by a 179-nucleotide untranslated region and a polyA+ tail. The axolotl C mu is divided into four typical domains (C mu 1-C mu 4) and can be aligned with the Xenopus C mu with an overall identity of 56% at the nucleotide level. Percent identities were particularly high between C mu 1 (59%) and C mu 4 (71%). The C-terminal 20-amino acid segment which constitutes the secretory part of the mu chain is strongly homologous to the equivalent sequences of chondrichthyans and of other tetrapods, including a conserved N-linked oligosaccharide, the penultimate cysteine and the C-terminal lysine. The four C mu domains of 13 vertebrate species ranging from chondrichthyans to mammals were aligned and compared at the amino acid level. The significant number of mu-specific residues which are conserved into each of the four C mu domains argues for a continuous line of evolution of the vertebrate mu chain. This notion was confirmed by the ability to reconstitute a consistent vertebrate evolution tree based on the phylogenic parsimony analysis of the C mu 4 sequences.
Assuntos
Ambystoma/imunologia , Evolução Biológica , DNA/química , Regiões Constantes de Imunoglobulina/química , Imunoglobulina M/química , Cadeias mu de Imunoglobulina/química , Ambystoma/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Sequência Conservada , Epitopos , Imunoglobulina M/genética , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , RNA Mensageiro/análise , Xenopus/imunologiaRESUMO
Systemic lupus erythematosus (SLE) is associated with immunoglobulin allotypes in several ethnic groups. In this study, we investigated the association of a Bst EII immunoglobulin heavy chain constant-region gene restriction fragment length polymorphism with SLE in patients from the US and Mexico. A 3-kb restriction fragment was observed with significantly decreased frequency in randomly selected Mexican SLE patients and in Mexican SLE patients in multiplex families. However, no such association was observed in SLE patients from the US. Thus, the absence of a 3.0-kb Bst EII restriction fragment from immunoglobulin heavy chain constant-region genes provides a marker for SLE in Mexican individuals.
Assuntos
Regiões Constantes de Imunoglobulina/genética , Cadeias Pesadas de Imunoglobulinas/genética , Lúpus Eritematoso Sistêmico/genética , Polimorfismo Genético/genética , Southern Blotting , Feminino , Humanos , Lúpus Eritematoso Sistêmico/epidemiologia , Masculino , México/epidemiologia , Linhagem , Polimorfismo de Fragmento de Restrição , Estados Unidos/epidemiologiaRESUMO
We have characterized immunoglobulin switch circular DNA in mice infected with the nematode parasite Nippostrongylus brasiliensis. Two kinds of circular DNA were identified in the lymph nodes as excision products of switch recombination of immunoglobulin heavy-chain constant region (CH) genes. One is a recombinant between C mu and C gamma 1 (gamma 1 circle), and the other is a recombinant between C gamma 1 and C epsilon (epsilon circle). In the epsilon circle, a short piece of switch mu (S mu) sequence was inserted between S epsilon and S gamma 1 sequences. The inserted S mu sequence could be a trace of the preceding switch from C mu to C gamma 1. These findings indicate that parasitic infection can induce class switch recombinations in a successive manner, first from C mu to C gamma 1, and then from C gamma 1 to C epsilon.
Assuntos
DNA Circular/genética , Cadeias Pesadas de Imunoglobulinas/genética , Região de Troca de Imunoglobulinas/genética , Cadeias lambda de Imunoglobulina/genética , Cadeias mu de Imunoglobulina/genética , Infecções por Nematoides/imunologia , Nippostrongylus/imunologia , Animais , Sequência de Bases , Células Cultivadas , Clonagem Molecular , Feminino , Regiões Constantes de Imunoglobulina/genética , Linfócitos/imunologia , Camundongos , Camundongos Endogâmicos BALB C , Dados de Sequência Molecular , Recombinação Genética , Baço/imunologiaRESUMO
Irradiation of DNA with UV light induces pyrimidine dimers and (6-4) photoproducts. The presence of one of these photolesions in the restriction site of a given endonuclease inhibits DNA cleavage and induces the formation of fragments by incomplete DNA digestion which appear as additional, facultative bands in Southern hybridization autoradiograms. The number and size of these fragments show a positive correlation with the UV dose. The response to UV light of immunoglobulin light-chain constant kappa and heavy-chain constant mu genes was analyzed with 2 specific probes. Constant kappa and mu genes when irradiated as part of the chromatin of living lymphocytes showed a UV sensitivity similar to that of naked DNA. The same genes from granulocytes had 50-60 times lower UV sensitivity. When cells were allowed to repair photolesions for 24 h the facultative bands from granulocytes disappeared indicating that these cells were able to remove photolesions from constant kappa and mu genes. Facultative bands from lymphocytes showed a smaller decrease of density after 24 h repair. This suggests that lymphocytes are less efficient than granulocytes in removing UV damage from constant kappa and mu genes.
Assuntos
Reparo do DNA , Genes de Imunoglobulinas/efeitos da radiação , Raios Ultravioleta , Autorradiografia , Southern Blotting , DNA/metabolismo , DNA/efeitos da radiação , Dano ao DNA , Enzimas de Restrição do DNA/metabolismo , Densitometria , Eletroforese em Gel de Ágar , Genes de Imunoglobulinas/genética , Granulócitos/efeitos da radiação , Humanos , Regiões Constantes de Imunoglobulina/genética , Regiões Constantes de Imunoglobulina/efeitos da radiação , Cadeias Pesadas de Imunoglobulinas/genética , Cadeias Pesadas de Imunoglobulinas/efeitos da radiação , Cadeias Leves de Imunoglobulina/genética , Cadeias Leves de Imunoglobulina/efeitos da radiação , Linfócitos/efeitos da radiação , SoluçõesRESUMO
Se estudió el efecto que dos formas de manipulación del sueño tiene sobre las inmunoglobulinas, la albúmina y el cortisol plasmáticos. Los 24 voluntarios sanos estudiados se asignaron al azar, a 3 grupos: en el primero se les privó totalmente de sueño (PST) durante 40 hr, y se recolectaron muestras plasmáticas antes de la manipulación experimental (BSL), durante la privación (TRANS) y en el seguimiento (POST). las muestras se tomaron a las 06:00 hr. A un segundo grupo de voluntarios se le privó del sueño de movimientos oculares rápidos (PSMOR-2); y al tercer grupo de sujetos se le privó de SMOR durante 6 noches (PSMOR-6). A estos dos grupos se les tomó sangre (en la situación basal y en la última nohe de manipulación del sueño), a las 06:00 hrs. En los resultados se obsevó que el grupo de PTS mostraba una disminución de los niveles de IgG en las condiciones TRANS y POST, sin cambios en el resto de las inmunoglobulinas o la albúmina, mientras que el cortisol se elevó en forma significativa en la situación TRANS. En el grupo PSMOR-2, únicamente se encontró una elevación de cortisol plasmático y, finalmente, en el grupo PSMOR-6 se detectó una elevación de la IgM
Assuntos
Humanos , Adulto , Masculino , Plasma/análise , Regiões Constantes de Imunoglobulina/imunologia , Albuminas/análise , Sistema Imunitário/imunologia , Sono REMRESUMO
We have analyzed the pattern of methylation of rearranged and germ line C kappa genes in DNA samples from human B-type chronic lymphatic leukemia lymphocytes and normal fibroblasts, and from granulocytes, T-, and non-T-lymphocytes separated from normal blood. C kappa alleles are flanked by one HpaII site on each side. Leukemic B-CLL DNA from five patients showed demethylation of these two sites in the productively rearranged allele and methylation of both sites in the nonexpressed allele whether rearranged or in germ-line configuration. Non-T-lymphocytes from normal individuals also showed part of the C kappa genes to have demethylation of both HpaII sites. On the other hand, C kappa genes from normal granulocytes, T-lymphocytes, and four of five fibroblast samples were methylated in one or both HpaII sites. We propose that in B-lymphocytes, demethylation of C kappa alleles is a specific event taking place in the expressed genes and being associated with an increased transcriptional activity of the gene. In addition to this specific demethylation, there is also an unspecific one that may appear in cells with silent C kappa genes and that do not modify the expression of the gene.