RRBC and EAC rosette formation after DNCB contact sensitization and cyclophosphamide treatment of guinea-pigs.

Rabbit erythrocyte (RRBC) and EAC rosette formation, for detection of T and B lymphocytes respectively, was studied in thymus, lymph nodes and peripheral blood of guinea-pigs. Using two different methods for preparation of RRBC rosette-forming cells (RFC) it was found that, without an incubation period at 37 degrees, a smaller part of the pool of T cells is detected which is particularly sensitive to cyclophosphamide (cy). RRBC rosette formation was studied for 2 weeks after treatment with one high dose of cy and appeared to be minimal in the thymus after 1 week and maximal in the lymph nodes at about day 3. EAC rosette formation was completely blocked by cy treatment. Four days after contact sensitization with 2,4-dinitrochlorobenzene (DNCB) no percentual increase was found in RRBC-RFC, suggesting a parallel increase of B and T cells in stimulated lymph nodes. Cytological screening of the rosettes at day 4 after DNCB showed that of the RRBC-RFC approximately 17 per cent were blast cells, while no difference was detected in the number of blast cells participating in EAC rosette formation as compared to the unstimulated lymph nodes. In contrast to RRBC-RFC the percentage of EAC-RFC in draining lymph nodes is increased after contact sensitization. The mechanism of this increase is discussed.