IMMUNOGLOBULIN AND T-CELL RECEPTOR GENE REARRANGEMENTS IN LESIONS OF MUCOSA-ASSOCIATED LYMPHOID-TISSUE

Twenty-one cases of mucosa-associated lymphoid tissue (MALT) lesions h ave been analyzed by Southern blot for immunoglobulin heavy chain (IgH ) and T-cell receptor beta chain (TcR(beta)) gene rearrangements (GR). The sites included colon, stomach, liver, nasopharynx, salivary and l acrimal gland, conjunctiva, tonsil, breast, and lung. Two of the lesio ns (parotid and conjunctiva) were malignant lymphomas and one case sho wed lymphoproliferative disorder. In the cases of malignant lymphomas, IgH GR were detected, and in the case of lymphoproliferative disorder , both IgH and TcR(beta) genes were rearranged. Among the remaining 18 cases, 9 showed inflammatory infiltrate, 3 lymphoid hyperplasia, 3 at ypical lymphoid hyperplasia, 1 carcinoma of the tonsil, 1 breast carci noma, and one was a sample of normal Peyer's patches. Among these 18 c ases, 3 showed TcR(beta) GR, 6 showed double IgH and TcR(beta) GR, and 4 IgH GR. Often multiple rearranged bands were observed, composing 10 -30% of the total DNA analyzed. The control tissue (Peyer's patches) s howed no GR. Because IgH and TcR(beta) GR are used to determine monocl onal proliferations of T and B lymphocytes, which occur in malignant l ymphomas, it is vital to determine the specificity of such a test. Thi s report stresses the fact that in MALT lesions false-positive results are not uncommon and therefore the results of IgH and TcR(beta) GR st udies have to be interpreted with caution. The presence of multiple GR in the inflammatory lesions indicates proliferation of minor monoclon al populations that can be detected with the use of Southern blot tech nology.