Immune system of swine: dissection of mononuclear leucocyte subpopulations by means of two-colour cytofluorometric analysis.

Expression of the differentiation antigen 8/1, a porcine leucocyte marker for which no counterpart is known as yet in other species, was tested in relation to the expression of surface Ig and the monocyte marker 74-22-15. B lymphocytes and T lymphocytes can be typified by the exclusive expression of surface Ig and 8/1, respectively, while all monocytes defined by the expression of the 74-22-15 antigen co-express 8/1 with the highest staining density observed for this marker. 8/1+ T lymphocyte subsets defined by the expression of CD4 and CD8 cell surface antigens differed in the expression of 8/1 with the staining density being high in CD4+ T lymphocytes, intermediate in CD8+ as well as in CD4+CD8+ T lymphocytes, and low in the CD4-CD8- subset. Practically all mononuclear leucocytes present in peripheral blood are included in the subpopulations defined by this kit of reagents, and thus it can be predicted that if mononuclear leucocytes which do not belong to any of these subpopulations exist at all, these must be rare and will not be accessible to an analysis without enrichment.