Trout immunoglobulin populations differing in light chains revealed by monoclonal antibodies

Monoclonal antibodies (MAbs) raised against trout immunoglobulin (Ig) recognize two independent Ig populations differing in the molecular weight of L chains. The trout Ig population recognized by MAb 2H9 represented congruent to 20% of the total Ig and contained L chains congruent to 26 kDa, whereas the trout Ig population defined by MAb 2A1 comprised 11% of the total Ig and possessed L chains congruent to 24 kDa. The determinants recognized by these MAbs reside on L chains as determined by ELISA using mildly reduced H and L chains. The size heterogeneity of the L chains was not due to differences in glycosylation. Partial peptide maps showed structural differences between both L chains. Both Ig populations were found in each of the 30 trout sera tested. These data extend the existence of L chains diversity in fish, recently described in catfish, to other teleosts.