This protein contains an unusual glycosylated proline-rich hinge region.
It has nothing to do with "red man syndrome", but an unusual side effect of vancomycin is a linear bullous dermatosis caused by this protein. People with a selective deficiency of this protein can undergo anaphylactic shock if transfused with whole blood. This protein can be selectively purified using Peptide M and SSL7, and it binds to CD89 on effector cells. This protein and complement factor 3 form complexes in blood vessel walls in Henoch-Schonlein purpura. This protein contains an unusual glycosylated proline-rich hinge region. M cells in the intestinal wall allow this protein and its binding partners to transcytose into (*) Peyer's patches. One section of this protein is encoded by the alpha-1 and alpha-2 regions of a particular locus, which are switched to using TGF-beta signaling. This protein polymerizes through the action of its J-chain. Colostrum is particularly rich in this protein, which is responsible for the passive immunity transmitted to infants through milk. For 10 points, name this antibody isotype that exists as a dimer, and is heavily present on mucosal surfaces and secretions.
It has nothing to do with "red man syndrome", but an unusual side effect of vancomycin is a linear bullous dermatosis caused by this protein.
IgA [or immunoglobulin A; prompt on immunoglobulin or antibody]