Light chain isotype‐associated suppression of normal plasma cell numbers in patients with multiple myeloma

The number of plasma cells in the lamina propria of the gut has been assessed in patients with multiple myeloma and other B‐cell neoplasms. The total number of these plasma cells was reduced in most patients with myelomatosis and one‐third of patients with lymphoplasmacytoid tumours. This reduction was not, however, seen in patients with other neoplasms of B‐cell origin, although hypogamma‐globulinaemia was common to all groups of patients. The depletion of gut plasma cell numbers was not uniform in myelomatosis patients. They showed selective loss of plasma cells with the same light chain isotype as that produced by the neoplastic clone.