The effect of pre-existing antibody on the result of immunization of mice with human B cell lines and transfected mouse cell lines

Abstract

Henry and Jerne (1968) described an interesting phenomenon, when SRBC's were used as antigen, the presence of IgG antibody prior to injection of antigen led to a suppressed response. In contrast, pre-existing IgM resulted in an increase of the primary immune response. The aims of this project were twofold, to determine if the same phenomenon is observed when using either human B cells or mouse transfected fibroblasts, as antigens; to study the feasibility of using IgM enhancement to improve the yield of antigen-specific hybridomas from mice against HLA-DP and DR. -- Studies were conducted using mice immunised either with a mouse transfectant cell line expressing HLA-DP (L25.4) or a human B cell line (RAJI). Preliminary experiments uncovered an unexpected reverse dose response when L25.4 cells were used as immunogen. Pre-treatment of mice with antibodies to monomorphic HLA-DP determinants increased and suppressed the responses as predicted; were statistically significant with both Raji and L25.4. In a second experiment, doubling of the IgM dose led to an unexpected diminution of the primary response against L25.4 and revealed that the half life of the administered IgM antibody appeared to be lengthened. -- Experiments were then conducted to determine the value of IgM pretreatment in the creation of hybridomas specific for HLA-DP and HLA-DR epitopes. Mice were pretreated with varying amounts of IgM antibody and then immunized. Three days later their spleens were removed, cells counted and fusions performed. Spleen size was found to be increased in a stepwise fashion with increasing doses of IgM past a previously described antigen induced plateau. The low dose of IgM produced spleens predominately composed of B cells, increasing the IgM dose decreased the B cells but increased the T cells. The IgM pretreated animals gave a 22.8% yield of specific hybridomas whereas the control group produced an 8%yield of specific hybridomas. Within the IgM pretreatment group, 96%of the selected hybrids originated from the low dosage group, indicating that there may exist an optimum pretreatment dose for IgM. These preliminary experiments support the potential of specific antibody pretreatment in the modulation of the primary response and the development of antigen-specific hybridomas.