No coin nor oath required. For personal study only.
Hahn: Dr. Gershon, would you clarify whether you meant that Ly-l cells and Ly-23 cells can function in different situations either as helpers or as suppressors, or whether it is the Ly-123 precursor that can function either way in each situation?
Cershon: There is no substantial evidence to indicate that the Ly-1 cell can do anything other than what it is preprogrammed to do, that is, to help B cells or to induce a DTH response. This Ly-l cell seems to have differentiated to a state where it has lost all its previous options, and its only decision is whether to turn on or not; after turning on with Con A, it still functions the same way. The same is true for Ly-2 positive cells, although, of course the function of the Ly-2 cell is quite different. However, there is a large population of cells that are not known to be committed to a single function, and it is in this population that all kinds of strange things happen. The Ly-123 cells can act as amplifier cells, but also seem to be able to act as a cell population that can differentiate into either helper or suppressor cells. The work ahead of us is to try to fractionate the Ly-123 population by some mechanism in order to determine whether the different effects they produce are stable cells, or Ly-123 just on a maturation path.
Williams: Since suppressor T cells are supposed to have Fc receptors for IgG and helper T-cell receptors for the Fc part of IgM, have you had an opportunity to look at these receptors in the subpopulations defined with respect to Ly typing?
Cershon: We haven't looked at the Fc receptor distribution among the cells. Bob Stout and the Herzenbergs in collaboration with Harvey Cantor showed that the Fc positivity cuts across all lines and a cell with a single function cannot be isolated by means of Fc receptors. No one I know has looked at subpopulations of Fc receptors on T cells in mice. There is also a problem in that the amount of Fc receptors on T cells will vary with their stage of differentiation. So this marker does not seem to have the advantage of the stability that the Ly markers have. But, we are looking at subpopulations of Fc receptors on macrophages and Erwin Diener's group is doing the same thing. There is a definite suggestion that subpopula-
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## Abstract From early on in evolution, organisms have had to protect themselves from pathogens. Mechanisms for discriminating βselfβ from βnonβselfβ evolved to accomplish this task, launching a long history of hostβpathogen coβevolution. Evolution of mechanisms of immune defense has resulted in a
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