378 IMMUNOGENETICS 



to antigens other than H-2, and, as far as H-2 is concerned, whether he has anyway of 

 visualizing the cell-to-cell reaction between the lymph node cells and the target cells. 



Dr. Winn: I would like to answer the last question first. No, we do not have any 

 techniques at all for visualizing the action between the specifically activated cells and 

 the target cells. As a matter of fact, we have considerable evidence that the cells 

 normally taken from draining nodes or spleen actually are immature in the sense that 

 they have not yet developed the capacity to react with the target cell. This is because 

 these cells are much more active on a cellular basis if they are transferred several days 

 before the test graft is applied. In a series of studies in which we mixed the target cells 

 with the immune, lymph-node cells and incubated them for very long periods of time 

 and then selectively destroyed the lymph-node cells with antiserum and complement, 

 the tumor cells grew as if they had never been in contact with the tissues at all. They 

 grew just as if they had been incubated with serum alone. I think that if you want to 

 visualize this reaction you have to find a source of the more mature cells, possibly in 

 the peripheral blood, or alternatively, one might provide some system of incubating 

 these cells from draining nodes and spleens in vivo in chambers or in tissue cultures and 

 testing them several days later. 



I think I would have to ask Dr. Snell to comment on the use of cytotoxic tests. 

 There is one system involving coisogenic strains in which we do have excellent com- 

 plement fixation. So far as I know, all the evidence indicates that a non-//-2 difference 

 is involved there. We also obtained a complement fixation with C3HK and C3H 

 serum which I believe has an H-\ difference. As far as using other cells is concerned, 

 lymph-node cells give far better reactions than any other tumor cells and any other 

 normal tissue cells. The cytotoxic test, I think you may be aware, is not equally 

 applicable to cells other than those from the lymph node. When the cellular prepara- 

 tion is made, a high percentage of the cells are already dead ; but this is the advantage 

 of complement fixation tests as they can be used on cells whether they are living or 

 dead. 



Dr. Snell: I might merely comment as to whether two of the systems which Dr. 

 Winn has employed are established as non-//-2 systems. The H-\ system is very 

 definitely, there is no question about it; but Dr. Winn did not get quite as clear results 

 with it as with the other system. 



Dr. Winn : It does not fix nearly as much complement. 



Dr. Snell: The other system, which does fix complement well, turned out to be 

 a new locus, H-5, but there is one additional test to run. 



Dr. Herzenberg : Dr. Owen, would you comment on the uses of labeled anti- 

 bodies? 



Dr. Owen: There have been many uses of labeled antibodies, for example in 

 localizing antigen, but only scattered applications of these techniques that could be 

 described as specifically immunogenetic. One example is the work of Masouredis, 857 

 who was able to distinguish a dosage effect in the Rh complex by the use of I 131 -labeled 

 antibody. 



