Antigenic competition between dengue and Coxsackie viruses for presentation to B cells by macrophages

Macrophages (M phi) pulsed with dengue type 2 (DV) and Coxsackie B4 (CoxB) viruses present antigen to B lymphocytes leading to their clonal expansion as detected by counting antigen-specific IgM antibody plaque-forming cells (PFC). The present study was undertaken to investigate the site for competition in M phi between the two heterologous antigens, DV and CoxB, for their presentation to B cells. It was observed that DV-pulsed M phi presented antigen to B cells in mice depleted of T cells by treatment with anti-Thy 1.2 monoclonal antibodies. The B cells could not be stimulated in absence of M phi in mice treated with silica. The PFC counts for both the antigens were inhibited when M phi were pulsed simultaneously with DV and CoxB. PFC counts were increased by 53-120% by predigesting the antigens by trypsin. Inhibition of DV-specific response by CoxB was abrogated by predigesting CoxB. A marked reduction in DV-specific PFC response was observed when CoxB was superimposed on M phi pulsed with DV 24 h earlier. CoxB-specific PFC counts were not affected by superimposing DV on M phi pulsed with CoxB 24 h earlier. PFC response to the antigen given to M phi before glutaraldehyde fixation was not affected while that for the antigen given to glutaraldehyde-fixed M phi was markedly depressed. It is concluded that the competition between DV and CoxB for antigen presentation to B cells occurs in M phi at the level of antigen processing.