Hybridomas made by fusing NSO (subline NSI Ag 4-1) mouse myeloma cells with lymph node cells from a calf immunized with sheep red blood cells failed to maintain antibody secretion in culture. However, when two of these hybridomas were selected in 8-azaguanine and then re-fused with immunized calf lymph node cells, several lines were obtained that secreted bovine Ig. One cloned line, producing bovine IgG1 (strongly lytic in the presence of rabbit complement and presumed to be an anti-Forssman) was maintained in culture for five months. Cytogenetic studies confirmed that the mouse/calf hybridomas lost bovine chromosomes as they proliferated, but that re-fusion increased the bovine complement from a mean of 5 (2 n) to 11 (2 n) bovine chromosomes per cell. It is proposed that the selected hybridoma lines may be suitable fusion partners for the production of further monoclonal bovine antibodies.

The effect of heat stress on antibody production to sheep red blood cells (SRBC) was investigated during three experiments using chicken lines selected over six generations for high (H) or low (L) plasma-antibody titer to SRBC after primary intramuscular immunization. The chickens were immunized 24 h after a heat-stress treatment (HS) of four periods of 30 min each at a temperature of 42 C with an intervening 30-min period at a temperature of 22 C. For the control treatment (CT), the chicks were handled the same, but at a temperature of 22 C. Antibody titers were measured on 3, 5, 7, 10, and 14 days postimmunization. The intramuscular immunizations, .25 mL of SRBC, were given in all three experiments; an additional intravenous immunization of .5 mL of 14% SRBC was given in Experiment 2 and of .5 mL of 5% SRBC in Experiment 3. A significant effect of the HS treatment on antibody titers (P less than .05 on Days 3, 5, 7, and 10 after immunization) was found only in Experiment 1. The titers decreased in the H line only. The differences between the H and L lines were significant (P less than .001) in all three experiments after both the intramuscular and the intravenous immunizations. Heat stress was found to have little or no effect on antibody production in the lines studied in the present experiments.

The effect of corticosterone on antibody production was studied in chicken lines selected for humoral immune response. 2. Twelve cockerels (33 days old) from lines selected for high or low antibody responses after immunisation with sheep red blood cells (SRBC) were implanted with mini-infusion pumps delivering corticosterone or vehicle continuously for 14 d. 3. Three days after implantation, the chickens were immunised intramuscularly with 0.25 ml packed SRBC. Blood samples were taken before implantation, before immunisation and 3, 5, 7 and 11 d after immunization. 4. Corticosterone infusion induced higher plasma corticosterone concentrations and heterophil/lymphocyte ratios than infusion of vehicle only. Growth was considerably depressed and relative weights of the thymus, bursa of Fabricius and spleen were less in the corticosterone-infused chickens. 5. An effect of corticosterone on antibody production could not be demonstrated, and differences between selection lines were unaffected.

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