114 DISCUSSION 



this material so one would expect labelled cells in any case and the 

 method may not turn out to be very helpful. 



Secondly, in addition to being unclear about the physiology of the 

 efferent end of the antibody reflex arc I admit to being equally so about 

 the afferent. I am wondering how you visualize this afferent mechan- 

 ism functioning. We have tried, with Elizabeth Sparrow, to repeat 

 Algire's work on the question of whether specific sensitization of ani- 

 mals follows grafting with homologous living cells in cell-impermeable 

 filter chambers. We have been able to achieve good survival of homo- 

 logous dissociated epidermal cells in filter chambers in the rabbit for 

 about 21 days or so, but there is no consistent evidence that these 

 chambers sensitize, which is a thorough confirmation of Algire (Algire, 

 G. H., Weaver, J. M. and Prehn, R. T. [1957]. Ann. N.Y. Acad. Set., 64, 

 1009). I would suspect that one could dismiss this as conclusive evidence 

 that antigens do not normally migrate freely outside of cells by saying 

 that the antigens under these circumstances have to traverse a difficult 

 and abnormal path to get out of the chamber. Perhaps they just don't 

 make it, for a variety of reasons, but are still normally released from 

 grafts as independent molecules. Would you admit the specula- 

 tion, however, that sensitization more probably takes place by a 

 handing on, from wandering lymphocytes, of the antigenic material 

 contained within them, to regional lymph nodes? Or doesn't this 

 fit? 



Billiiigham: I find the idea of circulating lymphoid cells getting 

 immunologically "primed" by peripherally located antigens very 

 attractive. 



Batchelor: How far down the gastrointestinal tract does this curious 

 property go ? Is it just localized to the pouch? 



BiUingham: It seems to be localized to the pouch. We have yet to 

 test the oesophagus. 



Brent: Dr. BiUingham has suggested that there is a physical barrier 

 which prevents a lymphatic drainage from being estabhshed. Would it 

 be too far-fetched to suggest the possibihty that there might be a chemi- 

 cal barrier of some kind ? Maybe there are enzymes present in the 

 connective tissue which inactivate the antigens as they come away from 

 the epitheUal cells. One way of approaching this problem would be 

 to extract isolated pieces of connective tissue to see whether such extracts 



