Granulocyte functions in sheep treated with 1-24 ACTH

GRANULOCYTE FUNCTIONS IN SHEEP TREATED WITH 1-24ACTH Paltrinieri S., Comazzi S., Sartorelli P., Agnes F., Istituto di Patologia Generale Veterinaria, via Celoria 10, Milano, Italy In order to verify if the increase in infectious diseases during stress could be due to an impairment in granulocyte functions, the different steps of the phagocytic process of neutrophil granulocytes (PMN) taken from sheep treated with 6,5 µg/Kg/b.w. of 1-24 ACTH (Synachten, Ciba) were investigated in vitro and the result compared with those obtained from untreated control sheep. PMN functions were tested before (T0) and 1 (T1), 2 (T2), 24 (T3) and 48 hours (T4) after 1,24 ACTH admnistration. The effectiveness of 1-24 ACTH administration was indicated by a neutrophilic leukocytosis and an increase in cortisol levels in treated animals Chemotaxis, measured using a modified Boyden chamber against omologous zymosan activated serum (ZAS) and recombinant human interleukin-8 (IL-8) showed a more homogeneous response to chemoattractants compared to controls. The ability of ingestion was not influenced by 1-24 ACTH administration: either in treated or in untreated sheep, in fact, 24 hours after the basal sampling was detectable an increase in phagocytosis of both inhert latex polystyrene beads and opsonized fluorescent yeasts. Adherence and respiratory burst were measured simultaneously in microtiter plates using a spectrophotometer to detect the superoxide production and the amount of acid phosphatase released from lysed adherent PMNs. Adhesive properties of neutrophils from treated sheep were increased when the highest cortisol levels were detectable, while the superoxide production, that increased at T2 in control sheep, did not show any increase in 1-24 ACTH treated sheep. The results presented here indicate that some steps of the phagocytic process are influenced in stressed animals. The “in vitro” increase of adherence might suggest an increased efficiency of the non-specific immune system, but the same finding has been interpreted by Arber et al. (1991) as a decreased “in vivo” ability of diapedesis throughout endothelial cells. In contrast, the depressed respiratory burst, compared to controls, might indicate a depressed bactericidal activity. Although stress “in vivo” has a more complex pattern than a simple administration of ACTH, the impairment of sheep PMN functions detected after 1-24 ACTH administration may contribute to the increased susceptibility to infectious diseases in stressed animals. Reference; Arber et al. (1991), Actaa haematologica, 86:20-24