Investigation of immunoglobulins in skin of the Antarctic teleost Trematomus bernacchii

The presence and production of IgM in the skin of the Antarctic teleost Trematomus bernacchii were investigated in this study. Immunoglobulins purified from cutaneous mucus and analysed by SDS-PAGE run under non-reducing and reducing conditions, were composed of heavy and light chains of 78 kDa and 25 kDa respectively, with a relative molecular mass of 830 kDa indicating that mucus IgM are tetramers as the serum IgM. Mature transcripts encoding the constant domains of both the secretory and membrane-bound Igμ chain were seen in T. bernacchii skin using a PCR strategy and the expression of the secretory Igμ chain in the skin was compared with that in other tissues by Real-time PCR. Cytological investigations revealed the presence of either immunoglobulins or their transcripts in occasional lymphocytes distributed close to the basal membrane. IgM once produced here, enters the filament-containing cells and is released into the mucus when these cells degenerate and detach from the epidermis. Our findings indicate that a cutaneous defence mechanism, functioning as anatomical and physiological barrier under subzero conditions, is present in this Antarctic species as an important component of the immune system.