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Neonatal Calf Serum Immunoregulation of Lymphocyte Blastogenic Responses

U. S. Department of Agriculture, Clay Center, NE 68933

Abstract

The ability of lymphocytes from newborn calves to undergo blastogenic responses to the mitogens Concanavalin A (Con A), phytohemagglutinin (PHA), or Pokeweed Mitogen (PWM), and immunomodulation of these responses by neonatal calf serum was assessed as a function of age. Lymphocytes were obtained from thymus, spleen, and mesenteric lymph nodes of 1-, 2- to 3-, 5- to 7-, and 9- to 10-d-old calves, aliquoted and incubated (± mitogens) in sera from 1-, 2-, 3-, or 7- to 10-d-old calves. Lymph-node lymphocytes responded least when cultured in sera from 1-d-old calves, regardless of mitogen or age of cell donor; the response increased as age of serum donor increased (P<.05). Splenic lymphocytes responded similarly (P<.005). However, when cultured in sera from older calves, splenic lymphocytes from older calves responded greater to PWM than did those from younger calves. Thymic lymphocytes responded minimally to PWM and PHA. Their response to Con A increased (P<.005) with age of serum donor calf, but the effect was greatest on lymphocytes from 5- to 7-d-old calves. Mixing experiments with varying ratios of 1-d-old calf serum: 10-d-old calf serum suggested that serum from 1-d-old calves contained suppressive activity. Serum Cortisol level (measured by radioimmunoassay) was 30 ± 4.6 ng/ml in calves at 6 h of age and declined to 5.5 ± 1.1 ng/ml by 10 d. Charcoal treatment to remove steroids did not enhance blastogenesis. Addition of Cortisol (50 ng/ml) to charcoal-treated sera resulted in inhibition of response to PHA, but no change in response to Con A or PWM. Further investigation is indicated to characterize this immunosuppressive activity and to establish its relationship to disease susceptibility.

¹ Roman L. Hruska U.S. Meat Anim. Res. Center, SE, ARS, USDA. Current address: SDS Biotech Corp., 7528 Auburn Road, Painesville, OH 44060.

² Mention of a trade name or companies does not constitute an implied warranty or endorsement by the USDA or the author.

³ The author thanks A. Campbell, R. Godtell, and B. Petitjean for technical assistance, R. Sigurdson and R. Johnson for assistance with calf handling and M. MacNeil for assistance in statistical analysis.

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