Simultaneous expression of CD4 and CD8 antigens by a substantial proportion of resting porcine T lymphocytes

The existence of four subpopulations in resting porcine T
lymphocytes is documented. In addition to the two known
subpopulations which are typified by a mutually exclusive
expression of either the CD8 or the CD4 differentiation antigen,
CD4-CD8+ and CD4+CD8- T lymphocytes, respectively, two unusual
subpopulations were prominent not only in peripheral blood, but
also in lymphoid tissues: CD4-CD8- T lymphocytes expressing neither
of these antigens and CD4+CD8+ T lymphocytes coexpressing both
antigens. While CD4+CD8+ lymphoblasts have been found also in other
species, resting T lymphocytes with that phenotype are without
precedent among all species analyzed to date. This unique
composition of the porcine T lymphocyte population has to be taken
into consideration when the swine is used as a large animal model
in experimental medicine.