Significant lymph node hyperplasia develops in transgenic mice carrying the HTLV-I-tax gene. These animals also develop pathological changes which share similarities with the human autoimmune disease, Sjogren's syndrome. Since lymph node hyperplasia developing to overt lymphoma is also characteristic of Sjogren's syndrome, this transgenic model may be useful in elucidating potential mechanisms by which lymph node hyperplasia and lymphoma may develop in this autoimmune disease. The tax transgene in this animal model has been shown to activate other growth-regulatory genes and the IL-2 alpha receptor subunit. The lymph node hyperplasia seen in these transgenic animals is composed of B-cells. The relationship between this B-cell proliferation and tax-induced cytokine production is being investigated.