Characterization of lymphocyte subtypes in scabietic skin lesions of naive and sensitized dogs.

We delineated the density of cells expressing CD4, CD8, CD21 and CD45RA antigens in the cellular infiltrates in the epidermis, dermis and follicular epithelium in scabietic skin lesions of naive hosts and sensitized hosts that expressed resistance to scabies infestation. No cells expressing CD21 (B-lymphocytes and follicular dendritic cells) were present in the epidermis and only a few were occasionally present in the dermis during both the first and second infestations. Naive T-cells (CD45RA+) and CD8+ cells (cytotoxic and suppressor T-lymphocytes) were present in varying densities in the infiltrates throughout the epidermis, dermis and follicular epithelium with no apparent differences in density and the rate of appearance between sensitizing and challenge infestations. CD4+ cells were abundant in fluctuating densities in the dermis, epidermis, and follicular epidermis during the sensitizing infestation and these cells became the dominant cell type early during the challenge infestation. The density of CD4+ cells in the infiltrate was much greater during the challenge than during the sensitization infestation. This population of CD4+ cells consisted of both T-helper/inducer cells and neutrophils and the large increase in their numbers during the challenge suggested they played a key role in the successful immune/inflammatory response that resulted in resistance to scabies infestation.