Autologous mixed lymphocyte reaction in human neonatal lymphocytes

Human neonatal mononuclear cells were examined to determine their ability to participate in an autologous mixed lymphocyte reaction (AMLR). Stimulator cells were isolated by plastic adherence and nylon wool adherence. The nylon wool-nonadherent cells were used as responder cells. In 10 of 10 neonatal samples and 6 of 7 adult samples, a significant AMLR was present when plastic-adherent cells were used as stimulators. Neonatal blood showed a mean increase in proliferation of 7.6 (3.6-14.9), while adult cultures showed a mean stimulation index of 11.8 (1.0-39.0). When nylon wool-adherent cells were used as stimulator cells, only 2 of 7 neonatal blood samples and 1 of 5 adult blood samples showed a significant AMLR. When recombinant interleukin 2 (IL-2) was added to AMLR cultures of plastic-adherent cells and nylon wool-nonadherent cells, a mean augmentation of 12.0 was seen in the neonatal AMLR, while the adult cultures were augmented by a mean response of 4.1. Addition of IL-2 to nylon wool-nonadherent cells alone produced a 5.9-fold increase in adult cells, while neonatal cells showed an 85.8-fold mean increase in proliferation. The results suggest that autoreactive T cells are present in neonatal blood and that these cells can be activated by plastic-adherent autologous cells. However, neonatal and adult nylon wool-adherent cells do not consistently activate autoreactive T cells.