Murine Fc receptors for IgG are redundant in facilitating presentation of immune complex derived antigen to CD8 super(+) T cells in vivo

Antigen(Ag)-immunoglobulin (Ig)G complexes (IC) are more efficiently processed and presented than soluble Ag. IC can bind to various cell types via different types of Fc-Receptors or, upon binding to complement factors, by complement receptors. Murine professional antigen-presenting cells (APC) express four types of Fc gamma Receptors (Fc gamma R) via which they are able to capture IC; three activating receptors (Fc gamma RI III and IV) and one inhibitory receptor (Fc gamma RII). It has been demonstrated that Fc gamma R play a pivotal role in facilitating the presentation of Ag derived from IC. Nonetheless, relative little information is available on the relative contribution of the activating or inhibitory Fc gamma R or complement to the presentation of immune-complexed Ag to CD8 super(+) T cells. To study the contribution of the different Fc gamma R and complement receptors in IC- facilitated Ag-presentation, we analyzed the ovalbumin(OVA)-specific CD8 super(+) T cell proliferation in Fc gamma R- and complement component 3 (C3)-deficient mice after subcutaneous injection of OVA-IC. Here we show that the efficient Ag- presentation was Fc gamma R-, but not C3-mediated, as it was inhibited in Fc gamma RI/II/III-deficient mice but unaffected in the C3-depleted mice. Moreover, Fc gamma RIV does not play a role under these conditions. However, no difference was found between wild-type and Fc gamma RI/III-deficient or wild-type and Fc gamma RII- deficient mice. These results indicate that Ag-presentation via the activating Fc gamma R is not enhanced in the absence of Fc gamma RII, and point to redundancy of the Fc gamma R, including Fc gamma RII, in the uptake and presentation of s.c. injected soluble IC to CD8 super(+) T cells.