FCGR3A and Arthritis: Also, according to Mancardi et al., at least IgG1 and IgG2 antibody isotypes, and two receptors, FcgRIIIA and FcgRIV, contribute to K/BxN-induced arthritis, and at least two cell types other than mast cells are required for this process—monocytes or macrophages, and neutrophils [15].