Aj. Ainsworth, A BETA-GLUCAN INHIBITABLE ZYMOSAN RECEPTOR ON CHANNEL CATFISH NEUTROPHILS, Veterinary immunology and immunopathology, 41(1-2), 1994, pp. 141-152
In mice and humans zymosan binds to the complement receptor three/Mac-
1 receptor; however, identification of this receptor in channel catfis
h (Ictalurus punctatus) has not been accomplished. Soluble fluorescein
isothiocyanate (FITC) conjugated beta-glucan, a component of zymosan,
was found to bind to channel catfish anterior kidney (AK) neutrophils
but not to B-lymphocytes. Serum activated zymosan (SAZ)-mediated chem
iluminescence responses of channel catfish AK neutrophils could be inh
ibited by beta-glucan but not by mannan, and inhibition of chemilumine
scence responses by beta-glucan was dose dependent. Similarly, phagocy
tosis of FITC-SAZ could be inhibited by beta-glucan in a dose-dependen
t manner. Treatment of channel catfish AK neutrophils with various con
centrations of trypsin resulted in inhibition of phagocytosis of FITC-
SAZ but not of Aeromonas hydrophila indicating that A. hydrophila phag
ocytosis was mediated by a trypsin-resistant receptor. Deleting serum
or using heat-inactivated serum in the mixtures for the chemiluminesce
nce and FITC-SAZ phagocytosis assays resulted in baseline readings. Th
ese data indicate that the beta-glucan component of zymosan is respons
ible for zymosan phagocytosis. Furthermore, the recognition of zymosan
by a specific receptor is evident based on trypsin sensitivity assays
. Based on these results it is proposed that a complement receptor 3,
Mac-1-like receptor, is present on channel catfish AK neutrophils.