228 J. R. BATCHELOR AND M. S. SILVERMAN 



efficiency in an environment containing excess humoral antibody. 

 Humoral antibody synthesis is known to continue during 

 enhanced tumour growth. It must be assumed that some 

 activated cells continue to synthesize and maintain an excess of 

 circulating humoral antibody. This excess has a dual influence, 

 discouraging effective action by cells in a state of specific hyper- 

 sensitivity and also inhibiting further lymphoid cells from becom- 

 ing hypersensitive. Our experience has been that the higher the 

 ratio of humoral antibody to sensitized cells, the greater the degree 

 of interference observed. But as toxicity of serum upon its 

 target is directly related to its concentration, the net result 

 represents a balance of these forces. 



It is possible that antiserum may directly affect sensitized cells, 

 but a more probable explanation would be that it combines with 

 aU the target cell determinants, denying the availabihty of these 

 sites to act as receptors for the adsorption of sensitized cells. This 

 imphes that the adsorption of sensitized cells to their specific 

 target is a reaction very similar to the adsorption of humoral anti- 

 body, and Boyden and Sorkin's conception of cytophilic antibody 

 may be relevant here (Boyden and Sorkin, i960). 



It is well known that lyophilized tissue is capable of immunizing 

 when administered in small doses, but following larger ones, 

 enhanced growth of transplants may be encouraged. It is not 

 easy to reconcile this with any theory of "blocked" immuni- 

 zation, but it could be assumed that this and certain other forms of 

 immunization favour the stimulation of a humoral response at the 

 expense of the hypersensitive cellular form. The view that 

 delayed hypersensitivity reactions tend to be suppressed by high 

 levels of humoral antibody is consistent with data from other 

 fields of immunology. For example, hyperimmunization 

 with the offending antigen is an accepted method of therapy 

 for patients suffering from delayed hypersensitivity reactions to 

 drugs and pollens. In guinea pigs, procedures designed to inhibit 

 the early development of humoral antibody synthesis — such as 



