Accumulation of CD25+ CD4+ T-cells in the draining lymph node during the elicitation phase of DNCB-induced contact hypersensitivity in lambs.

The elicitation phase of DNCB induced contact hypersensitivity in lambs was studied, and the presence of CD25+ cells in the lymph nodes draining the contact site was measured. Confocal laser scanning microscopy was used to capture images of two sets of triple immunofluorescence labellings. One set labelled CD25+, CD4+ and CD3+ cells, while the other labelled CD25+, VPM30+ and CD4+ cells. The CD25+ subpopulation labellings were assessed by area measurements in a morphometric protocol. The CD25+CD4+CD3+ cells were found to be increased in the DNCB treated group. This subpopulation of CD25+ cells comprised 75% of all CD25+ cells measured. The CD25+VPM30+CD4+ cells were also found to be increased in the DNCB group, but comprised only 17% of the total CD25+ cells measured. Since the VPM30 antibody detects an antigen found on activated T-cells, it was concluded that a substantial proportion of the triple CD25+CD4+CD3+ cells could represent a regulatory phenotype that may be active in suppressing the formation of effector immune cells in CHS of sheep.