Comparison of the allospecific and viral-specific immune responses to irradiated versus formaldehyde-fixed allogeneic Moloney lymphoma cells in CBA mice.

Two groups of adult CBA mice were immunized with 10-7 allogeneic Moloney lymphoma (YAC) cells. These YAC (H-2a) cells, which were either irradiated with 6000 R (Group i) or were formaldehyde fixed (Group II), were injected i.p. at weekly intervals for 3 weeks. Four days following the last injection, sera and lymphocytes were collected and tested in vitro for activity against either allospecific antigens (H-2d target cells) or viral-specific antigens, namely, Moloney leukemia virus (MLV). Both groups of animals developed measurable cellular and humoral immunity to the virally determined antigens. However, only the animals in Group i, immunized with irradiated cells, developed detectable immunity to H-2d. Immune and control lymphocytes were tested in microcytotoxicity tests and by 51Cr release. Antibody was assessed by complement-dependent cytotoxicity, indirect membrane immunofluorescence, virus neutralization, and antibody-dependent lymphocyte cytotoxicity. Group I serum, which had both anti-MLV and anti-H-2 antibodies, was absorbed with either living or formaldehyde-fixed YAC cells. The living cells were able to remove both H-2 and MLV antibodies. On the other hand, the formaldehyde-fixed cells removed no H-2 antibody but were able to remove MLV antibody, although less efficiently than living cells. These data indicate that formaldehyde fixation selectively impaired the H-2 antigens, leaving the viral antigenicity relatively intact. Differences between the immune responses to MLV-determined antigens and to H-2 antigens were demonstrated in many of the parallel in vitro tests.