RESUMEN
Antigen-specific T lymphocytes appear to recognize foreign antigens in the form of peptide fragments presented within the antigen-binding groove of class I or class II molecules encoded by the major histocompatibility complex (MHC). Alloreactive T cells also show specificity for MHC molecules, and various reports suggest that residues of the MHC molecules constitute at least part of the ligand to which alloreactive T-cell receptors bind. The X-ray crystal structure of the human MHC class I molecule, HLA-A2, has provided evidence to strengthen the argument that MHC-bound self-peptide might also contribute to such recognition. We now provide direct evidence for this, showing that at least some alloreactive cytotoxic T lymphocyte clones recognize peptide fragments derived from cytoplasmic proteins. We reasoned that if self-peptides were involved in allorecognition, then the sequence of some of these peptides could vary between species, resulting in species-restricted distribution of the relevant ligand(s). Several alloreactive cytotoxic T lymphocyte clones specific for H-2Kb, expressed by the murine cell line EL4, did not lyse a human-cell transfectant expressing the H-2Kb molecule (Jurkat-Kb cells). However, these clones were able to lyse Jurkat-Kb cells sensitized by preincubation with an EL4 cytoplasmic extract cleaved by cyanogen bromide. The sensitizing activity from this extract was destroyed by protease and appeared to be due to a peptide consisting of 10 to 15 amino acids.
Asunto(s)
Antígenos H-2/inmunología , Fragmentos de Péptidos/inmunología , Linfocitos T Citotóxicos/inmunología , Animales , Línea Celular , Células Clonales , Epítopos , HumanosRESUMEN
The frequency of diagnostic amniocentesis is increasing. Fetal bleeding and trauma have long been recognized to be complications of amniocentesis. For detection of fetomaternal bleeding, efficacy of modified Kleihauer-Betke staining and alpha-fetoprotein elevation in maternal blood was assessed. Preamniocentesis ultrasound scanning was found useful in reducing the incidence of fetomaternal bleeding and bloody taps. Elevation of alpha-fetoprotein was found to be a more sensitive indicator of fetomaternal bleeding than was modified Kleihauer-Betke staining. The use of alpha-fetoprotein to detect fetomaternal bleeding associated with amniocentesis is suggested for the identification of Rh-negative patients requiring anti-D gamma-globulin to prevent sensitization.