Serum IgM, MH class IIβ genotype and respiratory burst activity do not differbetween rainbow trout families displaying resistance or susceptibility to the coldwater pathogen, Flavobacterium psychrophilum.

A walleye dermal fibroblastoid cell line, WE‐skin11f, was established and characterized. WE‐skin11f was immunocytochemically positive for two known dermal fibroblast protein markers: vimentin and collagen I. At passage 26, WE‐skin11f cultures contained both diploid and aneuploid populations. Ascorbic acid was required to produce extracellular collagen I fibres. Both of the skin fibroblastoid cell lines, WE‐skin11f and rainbow trout‐derived RTHDF, were not as good as the walleye caudal fin fibroblastoid cell line, WE‐cfin11f, at forming abundant dense extracellular collagen matrices. The thermobiology of WE‐skin11f was similar to that of other walleye cell lines with 26°C showing best temperature for growth and 4°C showing no growth but 100% viability. The transcript levels of b2m and mhIa genes of the major histocompatibility class I receptor in WE‐skin11f were largely similar at all temperatures examined (4, 14, 20 and 26°C). Cortisol had a variety of effects on WE‐skin11f cells: growth inhibition, morphological change from fibroblastoid to epithelioid, and enhancement of barrier function. Treatment of WE‐skin11f cells with the physiologically relevant concentration of 100 ng/ml cortisol inhibited collagen I synthesis and matrix formation. Thus, WE‐skin11f cell line could be useful in fish dermatology, endocrinology, and immunology research.

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