ICOS proteins optimize T cell responses to foreign antigens, promoting proliferation, lymphokine secretion, upregulation of cell-cell interaction molecules, and efficient B cell antibody secretion. ICOS is essential for efficient communication of T cells and B cells and for normal antibody responses to T cell-dependent antigens. ICOS Protein, Mouse (C137S, C138S, HEK293, Fc) is the recombinant mouse-derived ICOS protein, expressed by HEK293 , with C-hFc labeled tag and C137S, C138S mutation.