Immunoresponses to Neisseria meningitidis epitopes: in vivo analysis of immunocompetent cells involved in suppression of secondary response to phosphorylcholine.

The immune response to phosphorylcholine (PC) antigens has been extensively studied in recent years. Neisseria meningitidis serogroup B M986 (NMB) was recently reported to induce a PC-specific plaque-forming cell (PFC) immuno-response in mice, a characteristic useful for the study of immunomodulating properties of N. meningitidis. With this technique, priming mice with low doses of NMB has been shown greatly to impair their ability, one month after priming, to mount an anti-PC response induced by NMB; this suppression is permanent, does not involve switching from IgM to another immunoglobulin class, transiently affects the T15 idiotype expression and is carrier specific. We report, based on an analysis of spleen cells from NMB-primed mice in an adoptive transfer model, that this suppression does not appear to be mediated by B lymphocytes nor does it seem to be under the direct control of T lymphocytes; rather, it involves radio-resistant cells. Additionally, our results show that NMB modulates the idiotype composition of the anti-phosphorylcholine response, probably by enhancing the expression of so called hapten-augmentable PFC. These results demonstrate that NMB can interfere effectively with the immune response in a variety of ways.