Reactive proliferative lesions in lymph nodes from rheumatoid arthritis patients. A clinicopathological and immunohistological study.

In 22 cases of rheumatoid arthritis (RA), including 4 cases of malignant RA (MRA), reactive proliferative lymph node lesions were studied clinicopathologically and immunohistochemically. This series included 5 males and 17 females. The period between disease onset and lymph node biopsy ranged from 3 months to 41 years. Generalized lymphadenopathy was noted in 13 cases and constitutional symptoms in 8. The histological findings characteristic of RA were 1) follicular hyperplasia with active germinal centers and 2) polyclonal plasma cell infiltration in the interfollicular area. Studies of intracytoplasmic immunoglobulin showed that gamma-heavy chain-expressing plasma cells were a major component in the interfollicular area in 17 RA cases. However, in 4 MRA cases, a prominent increase of mu chain-expressing plasma cells was recognized in the same area. In the 3 cases for which fresh tissue sections were stained with monoclonal antibodies against lymphocytes, we found that the majority of T cells in the interfollicular area had helper/inducer markers. The identical locations of the T cell population and plasma cells indicated that both played a role in the proliferation and/or differentiation of B cells in lymph nodes in RA.