Immunomodulating activity of meningococcal antigens.

A preparation of meningococcal antigens (MA) extracted in CaCl2, and containing mostly outer membrane proteins, was strongly mitogenic for murine B lymphocytes. Given to mice in vitro, MA markedly impaired subsequent in vivo T-cell responses of splenocytes. Suppression of normal T splenocytes in vitro occurred with both adherent (Ad) and nonadherent (NA) splenocytes from MA-sensitized mice. B cells were much less affected by the suppression induced by MA, and only Ad cells could convey in vitro the low level impairment of B-cell proliferation. Strong T-cell suppression associated with a B-cell mitogen is also produced by bacillus Calmette-Guérin (BCG) and Corynebacterium parvum. The possible role of these phenomena in meningococcal disease is discussed.