TRIM21-mediated immune signaling mechanisms play a role in infection by invading pathogens and in internalization of large, insoluble, antibody-bound antigens (even inanimate objects such as antibody-coated latex beads); indeed, transfection of antibody-coated latex beads causes TRIM21-induced activation of NF-κB, whereas transfection of antibodies or beads alone does not (2, 4, 50). This evidence concerns the gene TRIM21 and infection.