Effect of controlled antigenic stimulation on lymphocyte subsets in pigs and pig fetuses

The effect of controlled antigenic stimulation in immunologically virgin organisms,i.e. pig fetuses treated with NDCM (Nocardia delipidated cell mitogen) and germ-free (GF) piglets associated with a non-pathogenicE. coli O86, on peripheral blood lymphocyte subsets defined by the expression of CD5 and CD8 was studied by double color flow cytometry. Stimulation of both fetuses and GF piglets increased the frequency of CD8^low+ lymphocytes. A prominent subset of CD5⁻ CD8^low+ NK cells was present in GF andE. coli associated piglets and their frequency was slightly higher inE. coli associated animals. The most pronounced difference between stimulated and non-stimulated animals was in a relative proportion of an ill-defined lymphocyte subset with an unusual CD5^low+ CD8^low+ expression. Both NDCM injection into fetal blood circulation and association of GF piglets withE. coli resulted in a marked increase of frequency of CD5^low+ CD8^low+ lymphocytes in peripheral blood.