RESUMEN

Anti-CD45RA antibody defined by anti-2H4 monoclonal antibody has been reported to split CD4+T cells into two distinct subpopulations. CD45RA antigen is present on the surface of virtually more than 95% B lymphocytes in the purified tonsillar B-cell preparations. We examined the role of CD45RA antigen on human B-cell function using this antibody. The addition to anti-2H4 to tonsillar B cells inhibited the proliferative response induced by Staphylococcus aureus Cowan strain I(SAC) in a dose-dependent manner. Kinetic analysis indicated that anti-2H4 exerted its inhibitory effect when added within the first 24 h of culture initiation during a 72-h culture period. Anti-2H4 inhibited the transferrin receptor expression without interfering with the expression of the IL-2 receptor on SAC-stimulated B cells in a short-term culture. Anti-2H4 blocked the progress of SAC-stimulated B cells from the G1 to S phase of the cell cycle. These events suggested that anti-CD45RA MoAb inhibited the proliferative response by directly acting on B cells in the G1 phase. In addition, anti-CD45RA antibody also had a suppressive effect on early phase of B-cell differentiation. This effect appeared to be independent of its suppressive effect on proliferation, because anti-CD45RA did not inhibit the proliferative response of preactivated B cells with lymphokines. These studies suggested that the restricted epitope recognized by anti-2H4 antibody may be directly involved in regulatory function on B cells.

Asunto(s)

RESUMEN

Available data indicate that B cell proliferation is inhibited in chronic renal failure and this is due to excess blood levels of PTH. This defect may also affect immunoglobulin production. We examined production of IgG, IgM and IgA by B cells stimulated with Staphylococcus aureus Cowan I (SAC) or with pokeweed mitogen (PWM) after eight days of culture and evaluated the effect of PTH on this process in 34 hemodialysis patients and 44 normal subjects. IgG, IgM and IgA production by B cells from patients was lower (P less than 0.01) than by B cells from normal subjects. Both 1-34 and 1-84 PTH inhibited (P less than 0.01) immunoglobulin production by B cells from normal subjects and dialysis patients. However, this inhibitory effect was evident in dialysis patients only with the higher dose of PTH. The inhibition of immunoglobulin production by PTH occurred only when the hormone was added at the initiation of the B cell culture. Inactivation of PTH abolished its inhibitory effect on immunoglobulin production. Agents that stimulate cAMP production (forskolin, cholera toxin) and the cAMP analogue, 8-bromoadenosine 3',5' cyclic monophosphate inhibited immunoglobulin production by B cells from both normal and dialysis patients, and the degree of inhibition was not different between the two groups. The calcium inophore A23187 also inhibited IgG, IgA and IgM production by B cells from normal subjects and dialysis patients; there was no significant difference in the degree of inhibition between the two groups. The resting levels of cytosolic calcium in B cells of dialysis patients was significantly (P less than 0.01) higher than that of B cells from normal subjects. The data show that: (1) immunoglobulin production is impaired in dialysis patients; (2) B cells of dialysis patients have elevated resting levels of cytosolic calcium; (3) PTH inhibits IgG, IgA and IgM production and this effect is at least partly mediated by PTH-induced cAMP production and alterations in cytosolic calcium into B cells; (4) this inhibitory effect is mediated by events that affect initial stages of B cell proliferation and maturation; (5) the requirement for high dose of PTH for its inhibitory effect on B cells from dialysis patients is probably due to desensitization and/or down-regulation of PTH receptors on B cells. The results are consistent with the proposition that impaired immunoglobulin production by B cells from dialysis patients is at least partly due to the state of secondary hyperparathyroidism in these patients.

Asunto(s)

RESUMEN

Neonatal injection of mice with rabbit anti-micro antiserum has been shown to produce complete loss of direct and indirect plaque-forming responses to sheep erythrocytes as well as loss of serum IgM and severe depressions of all other serum immunoglobulins. Similar injection of anti-gamma1gamma2 or anti-gamma1 antibodies effects a loss of the indirect response but induces relatively minor alterations in serum Ig levels. Delaying initiation of anti-micro treatment until young adulthood results in a somewhat diminished effect on plaque-forming responses and serum Ig levels but triggers the release of high serum levels of an aberrant micro-bearing protein. Anti-micro suppression of genetically thymusless mice indicates that at least part of the target cells for suppression are bone marrow derived. A working hypothesis for the maturation of humoral antibody-producing cell lines as it relates to these data is discussed.

Asunto(s)

RESUMEN

Human sera have been examined for antibodies with specific reactivity for gammaE using the tanned cell hemagglutination test. Cells tanned with three different gammaE myeloma proteins provided a reproducible test system. Inhibition of agglutination reactions by gammaE proteins, but not by gammaG, gammaA, gammaM, or gammaD confirmed the specificity of these reactions. 8.5% of 304 serial serum samples obtained from miscellaneous hospitalized patients showed clear-cut anti-gamma-globulins with specificity for gammaE. In most of these instances no definite clinical history of concomitant allergic disorders could be obtained. 53% of 73 patients with well-established allergic disorders (hay fever, extrinsic asthma) showed serum anti-gamma-globulins with reactivity for gammaE. Some patients studied before and after desensitization to Bermuda grass allergen showed an increase in titer or a conversion from negative to positive reactions for anti-gammaE antibodies following several month courses of progressive desensitization. Gradient and gel filtration studies indicated that anti-gammaE globulins were 19S gammaM in all instances. No clear correlation was noted between quantitative serum gammaE levels and titer of anti-gammaE antibodies.19S serum fractions with anti-gammaE antibody activity did not release histamine from normal human peripheral blood leukocytes, whereas specific rabbit anti-gammaE antisera consistently induced leukocytic histamine release. Moreover, macroglobulin fractions with anti-gammaE activity did not block allergen-specific leukocyte histamine release induced by in vitro leukocyte challenge with allergens such as Bermuda grass and leukocytes from allergic donors. In some instances 19S human serum fractions with anti-gammaE activity appeared to potentiate histamine release when incubated concomitantly with specific allergen and leukocytes from allergic individuals.

Asunto(s)

RESUMEN

The suppressive effects of monospecific goat anti-mouse globulins on primary immunoglobulin class-specific plaque-forming cell responses in mouse spleen cell cultures were investigated. Anti-micro suppressed responses in all immunoglobulin classes, whereas anti-gamma(1) and anti-gamma(2) suppressed the gamma(1) and gamma(2) responses but not gammaM or gammaA responses, and anti-gammaA suppressed only gammaA responses. The mechanism of action of the anti-micro was studied in detail because of its suppression of responses in all immunoglobulin classes. The anti-micro was specific for micro-chain determinants; its activity was dose dependent, but was not mediated by killing cells with surface micro-chain determinants. Free gammaM but not gammaG myeloma proteins in solution effectively competed with micro-bearing cells for the anti-micro. An excess of anti-micro was necessary in the cultures for 48 hr to insure complete suppression of 5-day responses. However, after removal of excess anti-micro at 48 hr, responses could be stimulated by newly added antigen in cultures where incubation was prolonged to 7 days. Anti-micro was most effective when added at the initiation of cultures and had no suppressive effect when added at 48 hr. Excess antigen did not effectively compete with anti-micro for antigen receptors. Precursors of antibody-forming cells were shown to be the cell population where the suppressive activity of anti-micro was mediated. The experiments suggest that anti-micro combines with micro-chain determinants in antigen-specific receptors on the surfaces of antibody-forming cell precursors, prevents effective stimulation by antigen and subsequent antibody production. To explain suppression of responses in all Ig classes by anti-micro, several models were proposed. It is not possible to determine from the data whether stimulation of precursor cells with gammaG or gammaA receptors requires concommitant stimulation of separate cells with only gammaM receptors, or whether cells bearing gammaM receptors are precommitted to or differentiate into cells capable of synthesis of other Ig classes, or whether receptors of gammaM and another Ig class are present on some virgin precursors or the second Ig receptor appears after antigenic stimulation.

Asunto(s)

RESUMEN

Suppression of Ig class-specific PFC responses by class-specific antibody to mouse immunoglobulin was studied in cultures of spleen cells from immunized mice. In contrast to cultures from normal mice where anti-micro suppressed responses in all Ig classes, anti-micro had progressively less suppressive effect on gamma(1) and gamma(2) responses in cultures from immunized mice with time after immunization. This was most pronounced at 10 days after immunization when anti-micro suppressed gammaM and gammaA responses, but had no or slight effect on gamma(1) or gamma(2) responses which were still suppressed with anti-gamma(1) and anti-gamma(2). These changes in precursor cell susceptibility to anti-micro were antigen specific.

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)