Mitogenic activity of influenza virus and haemagglutinin

Abstract

Influenza A viruses behave as T cell-independent B cell mitogens in vitro. The magnitude of the proliferation induced varies with the haemagglutinin subtype of the virus, the order being H2 greater than H6 greater than H3 greater than H1 for Balb/c mice. H3 viruses are equally mitogenic for all strains of mice tested. In contrast, the mitogenic response to H2 and H6 viruses is controlled by the I-E subregion of the major histocompatibility complex. These viruses are mitogenic only for strains of mice that express surface I-E antigen (haplotypes a, d, k, p, r), and not for haplotypes b, f, q, s, which fail to synthesize a normal E alpha chain and do not express surface I-E antigen. Mitogenesis by H2 and H6 viruses may involve direct interaction of virus with I-E molecules on the B lymphocyte or an accessory cell, whereas mitogenesis by H3 viruses does not appear to involve I-E.