150
indicates the proteins being detected on fish lymphocytes were not on
all fish cells.
Therefore, assuming adequate specificity of the antisera and the
physiologic state of the labeled cells, the results obtained here
illustrate several important aspects of fish membrane immunoglobulins.
First, as previously described for other fish species (44,45,46,116),
nearly all bluegill blood, spleen, thymus, and anterior kidney lympho
cytes possess surface immunoglobulin determinants that appear capable
of "patching" and "capping" when complexed with anti-Ig. Secondly,
quantitation of these antigenic determinants indicated that bluegill
lymphocytes have similar amounts of membrane Ig regardless of the tissue
of origin and perhaps more importantly, that this amount was quite
similar to that demonstrated for mouse splenocytes (presumed 'v 50%
B-c.ells). It should be mentioned that this level is about 10 times that
reported by others (92) for mouse B cells. In all likelihood this
difference is attributable to the fact that the lysates used contained
undetermined amounts of unlabeled cytoplasmic Ig. Hence the values
reported here for bluegill and mice must be considered as approximations
Thirdly, in terms of the physicochemical properties of bluegill membrane
immunoglobulins, at least half of the immunoprecipitable membrane radio
activity was associated with a, 180,000 material and, hence, ressembles the
2H-2L chain covalently linked membrane Ig's found on lymphocytes of
higher animals. It should also be emphasized that, since the H-L
chain rations (in terms of radioactivity) precipitated with the two anti
sera were similar, it becomes highly likely that only one class of H
chains is present on bluegill lymphocytes. The finding of similar H-
like chain molecular weights for material isolated from bluegill