Antibody-mediated binding of fluorescent HIV Gag and influenza nucleoprotein tetramers to blood cells

Antibody-mediated elimination of foreign antigens contributes to immune protection from viral infection. We have generated phycoerythrin-conjugated HIV-1 Gag/p24 and influenza virus nucleoprotein tetramers for flow cytometric analysis of blood cell populations involved in antibody-mediated immunity. We show that in the presence of antigen-specific antibodies fluorescent antigen tetramers bound to different blood cell populations including granulocytes, monocytes and lymphocytes. Binding to B-lymphocytes was particularly efficient. The interaction was primarily mediated by complement. Fcγ receptor-mediated antigen binding by B-cells was significantly less effective. The study shows that fluorescent antigen tetramers are useful to quantify cell populations involved in complement- and Fcγ-mediated immune responses in viral infections.