Summary Immune functions were studied in male calves fed milk replacer (MR) containing 10 or 50 mg iron (Fe)/kg. Calves fed 10 mg Fe/kg MR developed marked hypoferremia and anemia, whereas serum‐Fe and haemoglobin concentration of calves fed 50 mg Fe/kg MR were normal. Growth performance was reduced, while feed/gain ratio, incidence of infections (especially pneumonias), febrile body temperatures and antibiotic treatments were higher in calves fed 10 than 50 mg Fe/kg MR (p<0.05). Whereas antibody production (to horse erythrocytes) and lymphocyte stimulation (by mitogens) were not significantly altered, cell‐mediated immunity (measured as cutaneous delayed‐type hypersensitivity reaction to dinitrofluoro‐benzene), number of neutrophils with phagocytic capacity, activity of the Fe‐containing enzyme myeloperoxidase, blood serum IgG concentration and the number and diameter of germinal centres as a measure of the number and production of B‐cells in cervical superficial lymphnodes in calves fed 10 mg Fe/kg MR were reduced when compared with calves fed 50 mg Fe/kg MR (p<0.05). In conclusion, severe Fe deficiency caused reduced growth performance, associated with and partly due to higher incidence of infections because of defective immune reactions.

Investigations on the W21 specificity showed that this antigen is expressed on lymphocytes and platelets but not on erythrocytes. The molecule carrying the antigen W21 moves in the cell membrane independently from ELA locus A and B encoded antigens, as observed in 'lysostripping'. The W21 specificity occurs with very different gene frequencies in various breeds. In informative families it segregates together with defined gene products of the MHC region.The data suggest strongly that the W21 specificity belongs to the ELA system as a class I gene product, but is governed by a separate locus than the known locus A and locus B allelic series.

Experiments were performed to determine the effects of the p-adrenergic agonist Ro 16-8714 on the immune system of finishing pigs fed an adequate or a low-protein diet. Growth rate, nitrogen and fat retention, body composition as well as spleen weight were influenced by both 0-agonist and/or protein level, as expected. However, lymphocyte stimulation with Concanavalin A and phytohemagglutinine in vitro or in vivo antibody production against horse red blood cells were not changed by the P-agonist in pigs fed sufficient or insufficient amounts of protein.