Anna Alessi

Anti-Ia reactivity in sera of untreated patients with active Hodgkin's disease.

The effect of sera from eight patients with Hodgkins disease on the autologous and allogeneic mixed lymphocyte response of normal individuals was examined. Sera from three patients with active disease caused marked inhibition of both autologous and allogeneic mixed lymphocyte reaction without inducing significant reduction of the phytohemagglutinin-induced proliferative response. The inhibitory activity of Hodgkins disease sera on the autologous mixed lymphocyte reaction was removed by adsorption with non-T, but not T, lymphocytes and it was correlated with the ability of such sera to block the binding of monoclonal anti-Ia antibody to Ia-positive target cells. Anti-Ia antibodies were detected in the same sera by double antibody radioimmunoassay and analysis on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, using 125I-labeled, partially purified, Ia antigens from two different human B-cell lines. This anti-Ia reactivity was strongly reduced or absent in sera taken from the same patients at the completion of multidrug chemotherapy.

Role of HLA class I and class II antigens in activation and differentiation of B cells

The monoclonal antibodies (MoAb) CR10-214, CR11-115, and Q1/28 to distinct monomorphic determinants of HLA class I antigens, the MoAb CL413 and PTF29.12 recognizing monomorphic determinants of HLA-DR antigens, the anti-HLA-DQw1 MoAb KS11, the anti-HLA-DPw1 MoAb B7/21, and the anti-HLA-DR,DP MoAb CR11-462 were tested for their ability to modulate human B-lymphocyte proliferation and maturation to IgM-forming cells. Purified tonsillar B cells were stimulated with Staphylococcus aureus bacteria of the Cowan first strain (SAC) or anti-human mu-chain xenoantibodies, as well as in growth factor- or T-cell-dependent activation cultures. The B-cell proliferative responses induced by SAC or by mitogenic concentrations of anti-mu-chain xenoantibodies were inhibited by some of the anti-HLA class I and anti-HLA class II monoclonal antibodies tested. The same antibodies were effective inhibitors of the proliferation of B cells stimulated with interferon-gamma (IFN-gamma) or interleukin-2 (IL-2) and with submitogenic concentrations of anti-mu-chain xenoantibodies. The proliferation induced by IL-2 of SAC-preactivated B cells was inhibited by some of the anti-HLA class II monoclonal antibodies, but not by the anti-HLA class I monoclonal antibodies tested. This inhibition appeared to reflect at least in part a direct effect on later events of the B-cell activation cascade, since some anti-HLA class II monoclonal antibodies still exerted considerable inhibitory activity when added together with IL-2 to SAC-preactivated B cells after the third day of culture. Anti HLA-DR, DQ, and DP monoclonal antibodies consistently inhibited the IgM production induced in B cells by T cells alone, T cells plus pokeweed mitogen (PWM), SAC plus IL-2, or IL-2 alone. In contrast, two of the three anti-HLA class I monoclonal antibodies tested inhibited the IgM production in cultures stimulated with SAC plus IL-2 and one the IgM production induced by IL-2 alone, but none of them had inhibitory effects on T-cell dependent IgM production. The results reported herein indicate that HLA class II molecules directly participate in different phases of the B-cell activation cascade. In addition, our data also suggest that HLA class I molecules can be involved in the events leading to B-cell proliferation and differentiation into immunoglobulin-secreting cells.

Different reactivity of activated human B cells to B-cell growth factor and interleukin 2 in the costimulation assay with anti-IgM antibody and in the preactivation assay with Staphylococcus bacteria

The two main assay systems which have been developed for the study of lymphokine-mediated human B-cell proliferation, i.e., the costimulation assay with anti-mu antibody and the preactivation assay with Staphylococcus aureus Cowan I (SAC) bacteria, were compared. Purified interleukin 2 (IL-2), obtained by the recombinant DNA technology (r-IL-2), enhanced the proliferative response of anti-mu-stimulated human B cells in the costimulation assay with anti-mu antibody and maintained the B-cell proliferation induced by preactivation with SAC bacteria. Although the majority of T-cell clones, established from normal peripheral blood T lymphocytes, showed production of both IL-2 and B-cell growth factor (BCGF) following phytohemagglutinin (PHA)-stimulation, some T-cell clones were found whose supernatants (PHA-SN), apparently free of IL-2, manifested strong BCGF activity in the costimulation assay with anti-mu antibody. However, the same clonal, IL-2-free, T-cell SN displayed no BCGF activity in the preactivation assay with SAC bacteria. When B cells were activated for 3 days with anti-mu antibody, followed by the addition of r-IL-2 or clonal T-cell SN containing BCGF for an additional 3 days, r-IL-2 showed the ability to maintain B-cell proliferation, whereas clonal SN containing BCGF had virtually no effect. These data indicate that the costimulation assay with anti-mu antibody explores the reactivity of normal human B cells to both BCGF and IL-2, whereas the preactivation assay with SAC bacteria, due to a shorter reactivity to BCGF of activated human B cells, essentially represents a probe for the study of IL-2-promoted B-cell proliferation.

The FcɛR2/CD23 antigen: A hallmark of chronic lymphocytic leukemia B cells

SummaryThe effect of different stimuli on the expression of the low-affinity receptor for the Fc fragment of IgE (FcɛR2/CD23) on peripheral blood B cells from patients with chronic lymphocytic leukemia (CLL) was investigated. CLL B cells cultured for 3 days in medium alone showed a progressive decrease of the FcɛR2/CD23 expression, while the addition to the cell cultures of IgE or interleukin-4 had a slackening effect on the decrease of the FcɛR2/CD23. In contrast, in the presence of interferon-γ the proportion of FcɛR2/CD23+ cells was more rapidly reduced compared to CLL B cells cultured in medium alone. Stimulation of CLL B cells withStaphylococcus aureus Cowan I (SAC) bacteria, which are able to enhance the expression of FcɛR2/CD23 on normal B cells, induced a rapid loss of the FcɛR2/CD23 from CLL B cells.

ALTERATIONS OF BOTH RESPONDER T CELLS AND STIMULATOR NON-T CELLS ARE RESPONSIBLE FOR ABNORMAL MIXED LYMPHOCYTE REACTION IN AGED HUMANS"

SummaryThe autologous and allogeneic mixed lymphocyte reactions of 15 young and 15 aged human adults were compared. Both autologous and allogeneic mixed lymphocyte reactions were significantly reduced in the aged group. T cells from aged adults displayed a reduced proliferative response to non-T cells of either aged or young adults. T cells from young adults also showed a reduced proliferative response to non-T cells from aged adults. Sera from aged adults, showing depression of autologous and allogeneic mixed lymphocyte reaction, did not exert any inhibitory effect on the autologous and allogeneic mixed reaction of lymphocytes from young donors. These data suggest that depression of mixed lymphocyte reaction in aged humans probably reflects intrinsic abnormalities of both responder T cells and stimulatory non-T cells.