Early Innate Immune Response of Mannose‐binding Lectin and Lysozyme in Juvenile Channel Catfish,Ictalurus punctatus

Innate immune proteins mannose‐binding lectin (MBL) and lysozyme were studied in channel catfish, Ictalurus punctatus, during two consecutive years at 2, 4, 6, 9, and 12 mos of age. Both groups maintained in indoor tanks in light/dark photoperiod at mean temperature 27 C. Dot‐blot enzyme linked immunosorbent assay (ELISA) for MBL and turbidometry lysozyme assay done to quantify the two innate proteins and means determined for two consecutive years. An increase in mean MBL was seen in 4‐mo catfish (26.9 ± 0.8 µg/mL) when compared with all other age groups. A decrease in mean MBL was seen in 6‐ and 9‐mo catfish when compared with all other age groups. Both 2‐mo (21 ± 1.4 µg/mL) and 12‐mo (19.9 ± 0.4 µg/mL) catfish were very similar in mean MBL concentrations. The greatest increase in mean lysozyme was seen at 4 mo (15 ± 5.0 µg/mL). Juvenile channel catfish could produce lysozyme at 2 mo equivalent to lysozyme concentrations found in 9‐ and 12‐mo catfish. The greatest increases for MBL and lysozyme were seen in 4‐mo catfish. Mean total protein of 26.7 mg/mL and mean albumin/globulin ratio of 0.7 were found for the two groups of channel catfish sera.