On the Role of T Lymphocytes in Stimulation of Humoral Immunity Induced by Peptidoglycan–Monomer Linked with Zinc

Effects of peptidoglycan linked with zinc (PGM–Zn) were investigated on plaque–forming cell (PFC) generation to sheep red blood cell (SRBC) and SRBC–unrelated antibody production in primary and secondary immune response in mice depleted in vivo of CD4+ and/or CD8+ T lymphocytes. PGM–Zn in nondepleted mice stimulated the PFC generation and IgM or IgG and IgG1 production in primary and secondary reaction. Single depletion of CD4 or CD8+ T cells did not change this ability. The effects of PGM–Zn after CD8+ depletion were even greater than those in nondepleted mice. Depletion of both T cell subsets, however, completely abrogated immunostimulatory effects of PGM on PFC generation (primary and secondary response), as well as on primary SRBC–unrelated antibody production, leaving only the increase of IgG in secondary response unchanged. Immunostimulatory effects and isotype switching to IgG1 and IgG2a correlated with the changes in splenic CD4+, CD8+, CD5+ cells, pointing to the regulatory role of these cells and/or their cytokines in PGM–Zn–induced immunostimulation. Altogether the data suggest that PGM–Zn may potentiate the costimulatory signals coming from activated T cells and act on B cells without the T cell help.