MUC1 and plasma cell myeloma: We speculated that MUC1 functions in modulating immune responses because of the findings that (a) soluble MUC1 inhibits the attachment of eosinophils to antibody-coated targets (36), (b) soluble MUC1 inhibits T cell proliferation (37), (c) MUC1 is expressed on human myeloma cells (38), and (d) MUC1 is also expressed on mouse granular metrial gland cells, which have a lymphocyte precursor (39).