HUMORAL IMMUNE-RESPONSE TO 2,4-DINITROPHENYL KEYHOLE LIMPET HEMOCYANIN IN ANTIGEN-FREE, GERM-FREE AND CONVENTIONAL BALB C MICE/

The B cell immune response to 2,4-dinitrophenyl (DNP) keyhole limpet h emocyanin was compared in antigen-free, germ-free and conventional BAL B/c mice. The numbers of total and of DNP-specific IgM-, IgG- and IgA- secreting cells in the spleen were determined by enzyme-linked immunos orbent plaque assays after primary, secondary and hyperimmunization. T hree days after primary immunization a peak of DNP-specific IgM-secret ing cells was seen in conventional mice only. However, this specific r esponse was accompanied by a rise in the total number of IgM-secreting cells. At day 6 after primary immunization the total number and the f requency of DNP-specific IgG-secreting cells were higher in antigen-fr ee mice, compared to germ-free and conventional mice. After secondary immunization in conventional mice only, a considerable bystander IgG r esponse was seen together with the DNP-specific IgG response. At the e nd of the secondary response 90% of all IgG-secreting cells were DNP s pecific in antigen-free mice, while the corresponding figure in germ-f ree and conventional mice was 63% and 14%, respectively. After hyperim munization, the absolute number of DNP-specific IgG-secreting cells in the spleen was 5-fold and 11-fold higher in antigen-free mice then in germ-free and conventional mice, respectively. Approximately 48% of a ll IgG-secreting cells were DNP specific in antigen-free mice,while th e corresponding figure in germ-free and conventional mice was 17% and 12%, respectively. The results show that the exogenous antigenic load of animals influences the immune response to newly introduced antigens . The higher absolute and relative numbers of antigen-specific IgG-sec reting cells after hyperimmunization in antigen-free mice compared to germ-free and conventional mice may provide a better source for antige n-specific B cells that eventually can be used for hybridoma productio n.