CD74 (EP167)

The CD74 antigen represents a membrane-bound subunit of the MHC Class II-associated invariant chain that is encoded by the gene located on Chromosome 5. The antibody recognizes nuclear and cytoplasmic antigens of MW 35 kD and 31 kD respectively. Anti-CD74 stains predominantly germinal center lymphocytes and those in the mantle cell region of the lymph node. It stains the cell membrane but a paranuclear globular labeling is also noted. Plasma cells are not labeled. Thymocytes are negative but dendritic cells are often labeled by anti-CD74. Anti-CD74 labels about 90% of low grade B-cell lymphomas and 20% of low grade T-cell lymphomas. In high-grade lymphomas the discriminatory power (B-cell vs. T-cell) is diminished. Reed-Sternberg cells are also labeled in approximately 60% of cases.1