Modulation of Fc gamma receptor II (CD32) expression of B lymphocytes to enhance antibody responses of young calves

This ongoing project involves characterization of receptors for IgG antibodies (Fc gamma receptors, FcgRII, aka CD32) on neonatal B lymphocytes, the cells responsible for active antibody production.  IgG antibodies (including passive maternal colostral antibodies) form complexes with antigens and inhibit the immune response to these

antigens by attaching to CD32 molecules on the B cell surface.  We had already demonstrated variation in

expression of FcgRII and other receptors in calves from birth to 6 months of age, using fluorescence activated cell scanning (FACs); and had identified several previously unknown isoforms of bovine FcgRII, with differences in function, by reverse-transcriptase / polymerase chain reaction (RT-PCR).  In this year GeXP^TM, a new method of

RT-PCR was used to compare the relative expression of the FcgRII b1 and b2 isoforms on B cells from neonatal

and older calves.  Expression of both these membrane bound isoforms was lower in neonates, and favored the b2 isoform, which inhibits new antibody production but does permit priming for future enhanced response.  In addition, we succeeded in characterizing the genes for CD21 and CD19, activating receptors on B cells, with potential to over-ride the down regulatory signals from CD32.  Also in this year, an in vitro protocol to measure Ca²⁺ flux by

flow cytometry (FACs) was adapted for detection of activation in bovine B cells to enable screening of compounds with potential to affect inhibitory and activating receptors.  These could be used in development of vaccines specifically targeted to neonates. Experiments were also initiated to examine the safety (reactogenicity) of two particle-based platforms for neonatal vaccines. This work moved the overall project considerably closer to the ultimate goal: to identify immune modulators, which activate neonatal B cells and/or minimize inhibition by