MULTIPLE REGULATION OF CARP (CYPRINUS-CARPIO L) MACROPHAGES AND NEUTROPHILIC GRANULOCYTES BY SERUM FACTORS - INFLUENCE OF INFECTION WITH ATYPICAL AEROMONAS-SALMONICIDA

Normal carp serum contains inhibitory and stimulatory factors for macr ophage and neutrophilic granulocyte respiratory burst activity. As sti mulatory factors were only effective in combination with phorbol myris tate actetate (PMA) activation, it is concluded that they are probably linked to protein kinase C activation. Both the stimulatory and inhib itory factors are heat stable. Macrophage- and neutrophilic granulocyt e-enriched cell fractions from the pronephros of carp had high respira tory burst- and high bactericidal in vitro responses to virulent atypi cal Aeromonas salmonicida bacteria. Serum factors were inhibitory for the A, salmonicida induced respiratory burst activity. No change in in hibitory or stimulatory serum factors could be observed during a 12-da y challenge experiment with A. salmonicida, or during a rechallenge of survivors from a previous sub-lethal infection. The sensitivity of ma crophages and neutrophilic granulocytes to stimulation of respiratory burst activity by PMA was not significantly altered. Culture supernata nts from PHA pre-treated lymphocytes stimulated the respiratory burst activity of macrophages and neutrophilic granulocytes suggesting that serum factors may partially be lymphocyte derived. Carp macrophages an d neutrophilic granulocytes undergo a multiple regulation by stimulato ry and inhibitory factors that will probably prevent the cells from ca using tissue damage during latent periods, but which enables rapid rea ction when fast induction of activity is required.