PTPRC and ocular melanoma: Lymphocytes were isolated from the RLN, pooled into groups of three animals, and stimulated with purified OM fraction from Leptospira. Both infected and control rats showed a significant increase (p < 0.005) in percentage of proliferating B cells (CD3−, CD19+, or B220+) when stimulated with 0.5 μg/ml OM antigen compared to no stimulant controls, Figure 5A, but no difference was observed between infected and control animals.