Developed M haemolytic plaque-forming cells in chickens.

Incorporation of rabbit anti-μ serum into agarose gels inhibited direct anti-SRBC PFCs using chicken complement, but developed equal numbers of indirect PFCs binding guinea-pig complement. The majority of attempts to demonstrate direct PFCs against HSA were unsuccessful, although low numbers of barely discernible PFCs were obtained by using HSA-SRBC sensitized with carbodiimide at room temperature; indirect PFCs were developed, however, by the anti-μ serum. During the primary response, developed anti-HSA PFCs could not be assigned to IgM or IgG classes using reduction and alkylation. Concanavalin A completely inhibited direct anti-SRBC and SIII PFCs, although developed γM PFCs were only inhibited partially. The identity of direct and anti-μ developed PFCs against SIII was demonstrated by the replica technique. None of the approaches applied provided any support for the existence of structural heterogeneity of IgM within the PFC population.