THE FACTS OF IMMUNITY 



type of antibody has, for obvious reasons, been done with 

 human sera, it is probable that a similar type of antibody can 

 be produced in rabbits. Sherman, Menzel and Seebohm 

 ( 1 950) immunized rabbits with ovalbumin precipitated with 

 alum, and found that their serum was capable of passively 

 sensitizing human skin. By fractional precipitation with 

 antigen they obtained a serum fraction incapable of pre- 

 cipitating with antigen but retaining the power to sensitize 

 human skin. Electrophoretic studies of sera from human 

 patients indicate that the activity is associated with one of 

 the faster moving gamma globulin fractions (Humphrey and 

 Porter, 1957). Some workers have considered the fraction 

 as essentially a y^-globulin (Loveless and Cann, 1955). Perhaps 

 the most important point from Humphrey's work is that the 

 antibody was concentrated in a sharp peak which led him to 

 suggest that it may be the product of some specific group of cells. 

 (3) Types (i) and (2) response are characteristically 

 associated with the production of specific circulating anti- 

 body. Type (3) differs sharply in that there is no evidence 

 that any circulating antibody is produced. The classical 

 example is tuberculin hypersensitivity, but it is highly 

 probable that similar reactions are concerned with skin 

 sensitization to simple chemicals and with homograft im- 

 munity. Further aspects of this type of immune response will 

 be discussed in the next section on congenital agamma- 

 globuhnaemia. A claim by Cole and Favour (1955) to have 

 obtained a serum fraction from tuberculous guinea-pigs 

 capable of transferring tuberculous hypersensitivity to normal 

 animals has not been confirmed. It has, however, been 

 abundantly confirmed that 'leucocytes', presumably lym- 

 phocytes, can transfer sensitization and the antibody is to 

 be regarded as a 'cell-borne' one. Jeter, Lawrence and 

 Seebohm (1957) have described a globulin of a 2 mobility 

 that can be extracted from competent cells and have evidence 

 that a subcellular component, possibly this alpha globulin, 

 is capable of transferring hypersensitivity. This raises the 



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