High spontaneous and mitogen-induced activity of mononuclear cells in lymph draining normal human skin

Lymphocytes in afferent lymph draining skin are derived from populations selected at the capillary level to enter the tissue space and which migrate spontaneously through the tissue to the initial lymphatics. These cells reveal a high spontaneous transformation rate in a 72 h culture. The mean 3H TdR incorporation was in a 24 h culture 2 times and in a 72 h culture 5 times higher than that of the peripheral blood mononuclear cells of the same subjects. The lymph cells responded significantly stronger to low concentrations of PHA, ConA and PWM than the blood cells. Also, the peak response of lymph cells was apparent at lower concentrations of mitogen in culture than of blood cells. The lymph cell population revealing a high spontaneous transformation rate was found to be the OKT4 enriched subset (induced/helper). The findings of a high spontaneous activation of lymphocytes which trafficked through the normal skin and defining this highly reactive subset as an OKT4-positive and strongly responsive to mitogens, reflect the in vivo immune events in the normal skin.