MHC‐ and non‐MHC‐encoded surface antigens of chicken lymphoid cells and erythrocytes recognized by polyclonal xeno‐, allo‐ and monoclonal antibodies

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Abstract
Surface antigens on chicken thymus and bursa cells were analyzed by immunoprecipitation using polyclonal and monoclonal antisera raised against (and specific for) thymus (ATS) or bursa (ABS) cells, respectively. The antigens identified were compared with those governed by the B‐F, B‐L and B‐G regions of the chicken major histocompatibility complex (B complex). Four proteins were precipitated from thymus cells by 2 polyclonal ATS: both antisera recognized molecules of apparent molecular mass of 172–182, 132–135, 75–76 kDa, and one antiserum in addition recognized a protein of 102 kDa. The 172–182 and 102‐kDa peaks were still demonstrable under reducing conditions indicating that they are composed of a single polypeptide chain, the other 2 were lost under reducing conditions, therefore, must be composed of smaller subunits. Of the 2 monoclonal ATS tested, one identified a single protein of 186 kDa and the other a 135‐kDa protein (in addition to 2 smaller molecules); whether these are the same as those precipitated by the polyclonal antisera remains to be determined as they behaved differently under reducing conditions. Proteins of 162 and 78–84 kDa were revealed by 2 polyclonal ABS under nonreducing conditions but the former may in one case be a polymer (it disappeared under reducing conditions) and in the other a single molecule. In addition molecules of 182 kDa were identified by one antiserum and of 84 and 60 kDa by the other under nonreducing conditions. Of the 4 monoclonal ABS only one identified a 200‐kDa protein: molecules of 115–125, 90–100, 48–52 and 40–43 kDa were also precipitated, all of which were reduced to smaller molecules. With 2 specific anti‐B‐F alloantisera we were able to precipitate the “conventional” B‐F antigen from red blood cell lysates of CB‐strain chickens resolving into a 40‐kDa peak and a light chain of about 12 kDa corresponding to β2 microglobulin. Precipitates from peripheral blood lymphocytes, bursa and thymus cells revealed an additional protein of 22 kDa. With 2 specific B‐L alloantisera two peaks of 33 kDa and 31 kDa were obtained from peripheral blood lymphocytes. Using anti‐B‐G alloantisera a double band corresponding to 47 and 42 kDa was seen under reducing conditions. There is no evidence from these data to indicate that the polyclonal and monoclonal antibodies are directed towards major histocompatibility complex antigens.