368 IMMUNOLOGICAL STUDIES 



cies of slime molds Gregg showed that new surface antigens ( as 

 illustrated in Fig. 4) are detected as the time of aggregation is 

 approached. Again one cannot conclude that the antigenic struc- 

 tures that are detected by the antibodies are necessarily the same 

 as those actually concerned in the cell adhesion. However, the 

 antisera have revealed a specific change in cell surface structure 

 correlating with the aggregation phenomenon. It can be expected 

 that this work will lead to extraction and characterization of the 

 specific substances involved. 



Since the previous discussion (Tyler, 1947) of the relation of 

 the auto-antibody concept to problems of embryonic differentia- 

 tion there have been a few pertinent, if not critical, experiments 

 on the subject. Mention was made on p. 348 of work showing 

 the detection of specific adult tissue antigens at stages prior to 

 visible differentiation. Their time of origin (or increase to detect- 

 able amounts) correlates in some cases with the time that the 

 embryonic tissue becomes "determined." In one particular case, 

 lens protein, experimental induction of the antigen has been re- 

 ported (Woerdeman, 1953a,b, 1955) through action of optic 

 vesicle extract on extracts of competent ectoderm. 



More particularly the question may be raised as to whether or 

 not processes of induction and detennination can be influenced 

 in specific fashion by substances that can also be described as 

 natural auto-anti]:)odics, extractable from the same organism. 

 There is, as yet, no direct experimental evidence concerning this, 

 nor, for that matter, concerning possible specific action of im- 

 mune antibodies on these processes. As noted above the work 

 with immune antisera has, so far, related to cytotoxic or generally 

 lethal effects in which action on specific de\'elopmental processes 

 are not immediately evident. Changes in cell type would be one 

 of the effects one might seek to obtain. Such changes have been 

 frequently described in experiments with microorganisms gi^own 

 in immune sera (cf. Dubos, 1946), although it is often uncertain 

 to what extent this is due to selection of variants not inhibited by 

 the antibodies. Selection is not involved in the experiments on 

 Parameciinn by Sonneborn (1948, 1950; cf. Beale, 1952) who 

 showed the induction of changes in antigenicity by means of 



