Stimulation of human peripheral blood mononuclear cells with anti-CD3 monoclonal antibody vs IL2: disparate effects on T cell-dependent B cell differentiation despite similar effects on generation of unrestricted cytolytic activity.

Despite their each inducing MHC-unrestricted cytolytic activity in overnight PBMC cultures mediated predominantly by CD56+ non-T cells, anti-CD3 mAb and rIL2 induce diametrically opposite effects on subsequent polyclonal T cell-dependent B cell differentiation. When added to fresh autologous PBMC, irradiated anti-CD3-stimulated PBMC inhibit generation of Ig-secreting cells (IgSC) in the secondary cultures, whereas irradiated rIL2-stimulated PBMC enhance IgSC generation. Neither carryover of the respective stimuli nor quantitative differences in levels of cytolytic activity against Daudi cells, autologous PBMC, or autologous activated B cells can explain the dichotomous anti-CD3- vs rIL2-induced effects on B cell differentiation. For both anti-CD3- and rIL2-induced effects on B cell differentiation, CD56- cells, including CD4+ and CD8+ cells, play a more dominant role than they do in generation of MHC-unrestricted cytolytic activity. In addition, although rIL2-induced enhancement of IgSC generation is insensitive to monocyte depletion by plastic adherence or by treatment with leucine methyl ester, anti-CD3-induced inhibition of IgSC generation is highly sensitive to monocyte depletion, indicating that, at least for anti-CD3-induced inhibition, multiple cell populations are required to generate the functional effect. Taken together, these results indicate that differences in the means of generating in vitro tumoricidal activity may have profound ramifications for non-cytotoxic immune parameters, such as B cell differentiation. Not only might this be an important issue to address in adoptive immunotherapy protocols for cancer patients but also adoptive immunotherapy might be applicable to certain autoimmune disorders if the ability to inhibit B cell differentiation could be channeled against the pathogenic antibody-producing B cells.