Costimulatory activity of inactivated influenza virus in response of humanperipheral blood mononuclear cells to phytohemagglutinin A and anti-CD3 antibody

We tested the effect of inactivated influenza A virus on the response of hu man T lymphocytes to several stimuli, Our results demonstrate that the resp onse to both phytohemagglutinin A (PHA) and anti-CD3 was substantially enha nced by pre-exposure of peripheral blood mononuclear cells (PBMC) to heat-i nactivated viral particles, whereas no effect was noted on the proliferativ e response of PBMC to IL-2, In addition to cell proliferation, exposure of PBMC to viral particles increased the secretion of interferon (IFN)-gamma d uring stimulation with anti-CD3 antibody and PHA, The costimulatory effect of influenza A virus was reduced by 40% in the presence of 0.1 mM sialic ac id. The possible mechanisms involved in the costimulatory effects of influe nza A virus are discussed.