Perforin expression can define CD8 positive lymphocyte subsets in pigs allowing phenotypic and functional analysis of Natural Killer, Cytotoxic T, Natural Killer T and MHC un-restricted cytotoxic T-cells

In this study we have used the expression of perform to characterize subsets of porcine cytotoxic lymphocytes. Perform positive lymphocytes expressed both CD2 and CD8 alpha, most were small dense lymphocytes (SDL) and up to 90% were CD3 negative. However, the numbers of perforin positive T-cells increased with the age of the animal and their populations increased after specific antigen stimulation in vitro. The remaining perform positive lymphocytes were large and granular and contained more CD3(+)CD5(+)CD6(+) T-cells (-40%) of which a substantial proportion also co-expressed CD4. Perform was expressed in subpopulations of both CD8 alpha alpha and CD8 alpha beta lymphocytes, but was not expressed in gamma delta T-cells or monocyte/macrophages. The perform positive CD3(-) Subset was phenotypically homogeneous and defined as CD5(-)CD6(-)CD8 beta(-)CD16(+)CD11b(+). This Population had NK activity and expressed mRNA for the NK receptor NKG2D, and adaptors DAP10 and DAP12. Perforin positive T-cells (CD3(+)) Could be divided into at least three subsets. The first subset was CD4(-)CD5(+)CD6(+)CD11b(-)CD16(-) most were small dense lymphocytes with cytotoxic T-cell activity but not all expressed CD8 beta. The second Subset was mainly observed in the large granular lymphocytes. Their phenotype was CD4(+)CD5(+)CD6(+)CD8 beta(+)CD11b(-)D16(-) and also showed functional CTL activity. Thus not all of double positive T-cells are memory helper T-cells. The third subset did not express the T-cell co-receptor CD6, but up to half of them expressed another T-cell co-receptor CD5. The majority of this subset expressed CD11b and CD16, thus the third perform positive T-cell Subset was CD3(+)CD4(-)CD5(+)CD6(-)CD8 beta(+/-)CD11b(+)CD16(+), and possessed MHC-unrestricted cytotoxicity and LAK activity. (c) 2005 Elsevier B.V. All rights reserved.