Ontogeny of PHA and con A responses in the fetal lamb

Mitogenic reactivity of mononuclear cells isolated from thymus, spleen and umbilical cord blood of pig foetuses

The in vitro mitogenic reactivity of mononuclear cells from the thymus, spleen and umbilical cord blood of Danish Landrace pig foetuses ranging in gestational age (GA) from 48 to 112 days was monitored by means of a microculture lymphocyte transformation test (LTT). Dose-response profiles for concanavalin A (Con A), pokeweed mitogen (PWM) and leucoagglutinin (LAG) were set up for the various age-groups and the results showed that the onset and development of mitogenic reactivity in the pig foetus is age-related. The results indicate the occurrence of mitogen responsive cells in the thymus and cord blood at 48 days GA and in the spleen at 54 days but statistically significant reactivity (p less than 0.01) for the various tissues could only be demonstrated at later stages of gestation. Thymus cells from all foetuses ranging in GA from 54 to 112 days exhibited significant reactivity to Con A, PWM and LAG. While the first detectable definite response of spleen cells was seen at 60 days GA when 50% of the foetuses exhibited significant reactivity to the 3 mitogens, spleen cells from all foetuses beyond that age responded significantly. Cord blood cells from only 50% of the foetuses of 60 and 70 days GA responded significantly to Con A and PWM but after this stage, cord blood cells from all foetuses did. The first significant response of cord blood cells to LAG was seen at 70 days GA but only in 50% of the foetuses and it was not until 100 days GA that significant reactivity to LAG was detected in all foetuses.

Ontogeny of T-cell mitogen response in Lewis rats: I. Culture conditions and developmental patterns

Spleen and thymus cells from female Lewis rats 2 to 220 days old were cultured with phytohemagglutinin (PHA) or Concanavalin A (Con A). The optimal dose of Con A for mitogenesis ranged from 1 microgram/ml for suckling rats to 125 micrograms/ml for adult rats. Thymus cells differed from spleen cells in that they required 72 hours for maximum thymidine incorporation; whereas spleen cells attained maximum incorporation within 48 hours. Thymidine uptake in unstimulated spleen cell cultures was high in the neonate and decreased with age. Maximum splenic cell responses to Con A increased from very low levels in the 2-day old to adult levels by 3 weeks coincident with weaning. Maximum PHA responses of splenocytes matured more slowly, reaching adult levels by 8 weeks. Thymus cell responses to Con A and PHA were mature from birth.