B cell lymphoproliferation in spontaneously diabetic BB Wistar rats.

Ninety-six spontaneously diabetic BB Wistar rats were maintained for their natural life span and, at death, were autopsied together with 86 age-and sex-matched non-diabetic BB control rats. A 15% incidence of abdominal B cell lymphoproliferative lesions was documented in the diabetic rats compared with 1% incidence in the non-diabetic rats (p less than 0.005). The B cell lymphoproliferative process included minute mesenteric and omental aggregates of plasma cells and small lymphocytes (one rat), atypical partially fibrotic lymphoproliferative mesenteric nodules (three rats), and malignant lymphoma with features of immunoblastic sarcoma (eight rats) or plasma cell lymphoma (two rats). Cytoplasmic immunoglobulin was demonstrated in two of the four lymphomas examined by the peroxidase-antiperoxidase technique, thus confirming their B cell derivation. The striking incidence of B cell lymphoproliferation in this diabetic population is additional evidence of altered immunity in this animal model of insulin-dependent diabetes mellitus.