TEMPORAL CHANGES IN THE POPULATIONS OF IMMUNE CELLS AT THE SITE OF EXPERIMENTAL DERMATOPHILUS-CONGOLENSIS INFECTION IN MICE AND SHEEP

The temporal patterns of dermal immune cell influx were compared in mi ce and sheep, species reputedly resistant and susceptible, respectivel y, to infection with Dermatophilus congolensis. In both species, the r esponse involved early mast cell degranulation, vasodilatation and an influx of dendritic cells which accumulated and apparently differentia ted beneath the infected epidermis. A concomitant dermal invasion by n eutrophils and T and B lymphocytes led to epidermal infiltration, part icularly by neutrophils and thence to the formation of the surface sca b. Hypertrophy of the epidermis also indicates keratinocyte involvemen t in the host response. The duration of the response, however, was con siderably shorter in the mouse (about 5 days) and B cells were the pre dominant lymphocyte under and adjacent to the lesion. During the more protracted response in the sheep (> 21 days), T cells, including T19 a ntigen + gamma delta T cells, outnumbered B cells.