Abstract
The neonate (NB) is susceptible to severe infection with intracellular pathogens such as Toxoplasma gondii (T), resistance to which is mediated by lymphokine (MAF) induced macrophage (Mφ) activation. We have previously reported decreased production of MAF by NB lymphocytes from cord and peripheral blood, decreased responsiveness of newborn Mφ to newborn but not to adult MAF, and that MAF appears to be γ-interferon. Since γ-interferon production is IL2 dependent, we assayed IL2 production by Con A stimulated cord and adult blood mononuclear cells (MC). MC supernatants were assayed for IL2 by measuring 3H-thymidine incorporation by an IL2 dependent CTLL cell line. Although lymphocyte transformation was comparable (Adult = 37822 ± 5795, NB = 38418 ± 2105 cpm, n=11), NB lymphocytes produced more IL2 (Adult= 543 ± 126, NB = 2414 ± 631 units/ml, n = 11, p < 0.005). In contrast, NB sups did not inhibit replication of T in Mφ (T per vacuole at 20h-control = 5.0 ± .3, + NB sups = 4.2 ± .3, NS) whereas adult sups did (T/vacuole = 2.9 ± .2, p < 0.05, n = 3). Unstimulated cord and adult MC did not release IL2 or MAF. These results suggest a disassociation between IL2 production and release of MAF by cord lymphocytes, which may contribute to the NB's susceptibility to infections with intracellular pathogens.
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