IMMUNOPROLIFERATIVE SMALL-INTESTINAL DISEASE AND B-CELL MALT LYMPHOMAOF THE DIGESTIVE-TRACT

Immunoproliferative small intestinal disease (originally called Medite rranean lymphoma and subsequently alpha chain disease) is a slowly pro gressive low grade primary small intestinal B-cell lymphoma characteri zed by the synthesis of a truncated alpha heavy chain without light ch ain by the neoplastic cells. The histological features of IPSID and lo w grade primary gastric B-cell lymphoma are closely similar and recapi tulate the those of Peyer's patches. This observation has led to the m ucosa associated lymphoid tissue (MALT) lymphoma concept which encompa sses a group of extranodal lymphomas including IPSID and primary gastr ic lymphoma. Unlike nodal low-grade B-cell lymphomas, IPSID and low gr ade gastric lymphoma remain localized to their sites of origin for pro longed periods. One possible explanation for this is that the growth o f these lymphomas is influenced by a local antigen. This is supported by reports of clinical remissions induced in IPSID following steriliza tion of the small intestine using broad spectrum antibiotics. Similar findings have been reported in low grade gastric lymphoma following er adication of Helicobacter pylori which is almost invariably present in the patients' stomachs. Laboratory experiments have shown that the gr owth of lymphomatous B-cells is stimulated via H. pylori specific T-ce lls. Further work is required to identify the antigen(s) operative in IPSID and, possibly, other low grade B-cell lymphomas.