Pathways of signal transduction in teleost nonspecific cytotoxic cells

In the present study evidence is presented that both a putative "receptor" binding monoclonal antibody (mAb) and the calcium ionophore A23187, either singly or together, increase receptor expression and lysis of IM-9 target cells by catfish NCC. NCC activity against IM-9 target cells was increased 55% after 1 h mAb treatment. Receptor expression determined by flow cytometry increased 95% following 18-h treatment. A23187 treatment of NCC produced greater than 200% increases in receptor expression. Combined treatments of NCC with 10^-4 M A23187 and 10^-7 M PMA however augmented receptor expression only 22% above that produced by A23187 alone. MAb and A23187 comodulated cytotoxicity by a 65% increase over ionophore treatment alone. MAb and 10^-10 M PMA comodulation produced only 10.6% increases in cytotoxicity compared to mAb. These data demonstrate that the moiety on NCC recognized by 5C6 may provide an activation signal for increased cytotoxicity and receptor expression. Calcium ionophore, either singly or together with mAb, provided an even stronger activation signal for increased lysis and receptor expression.