Multiple bovine Fc gamma RIIb sub-isoforms generated by alternative splicing

作者：Firth Matthew A^*; Chattha Kuldeep S; Hodgins Douglas C; Shewen Patricia E

来源：Veterinary Immunology and Immunopathology, 2010, 135(1-2): 43-51.

DOI：10.1016/j.vetimm.2009.10.029

• CD32
• Bovine
• Neonatal
• Fc gamma RIIb

Receptors for the Fc portion of immunoglobulin molecules (FcR) provide an important and vital link between circulating antibody and cellular effector functions. These receptors have been well characterized in human and murine species, however few of these receptors have been investigated in livestock. Fc gamma RII (CD32) is an FcR previously shown in mice and humans to exist in multiple isoforms, both activating (Fc gamma RIIa, Fc gamma RIIc) and inhibitory (Fc gamma RIIb), on a wide variety of cells including B cells, T cells, dendritic cells, monocytes, macrophages and platelets. On B cells, Fc gamma RIIb acts to suppress cell activation and immunoglobulin production by means of an intracellular immunoreceptor tyrosine-based inhibitory motif signaling domain. Two sub-isoforms of Fc gamma RIIb, designated b1 and b2, distinguished by the inclusion of an additional cytoplasmic exon in the b1 form, have been demonstrated in humans and mice, whereas only one sequence corresponding to the human and mouse b2 isoform has been identified in cattle. In this study, the expression profile of Fc gamma RIIb in bovine blood mononuclear cells was characterized by collecting blood samples from mature cattle of dairy and beef breeds, and determining their Fc gamma RIIb mRNA expression profile by RT-PCR. Analysis revealed the presence of two uncharacterized bovine Fc gamma RIIb transcripts in addition to the single previously published transcript. Analysis of the first unknown transcript revealed high homology with published human and murine Fc gamma RIIb1 sequences. This transcript was present in all cell types examined, with little variation in primary sequence between individuals or among breeds. The second unknown sequence was found to be homologous to the murine Fc gamma RIIb3 (IgG-binding protein or soluble Fc gamma R in humans) sequence. This transcript appears to have a much more limited expression profile, which may indicate that expression varies with the cellular activation-state of the cell. These results indicate that cattle, like humans and mice, express multiple sub-isoforms of Fc gamma RIIb. These findings add further complexity to the regulation of IgG-mediated immunity and provide new insight into the role Fc receptors play in antigen acquisition and presentation in cattle.

• 出版日期2010-5-15