270 RECEPTORS OF THE THIRD ORDER 



This action again shows the close relation between toxins 

 and enzymes. Complement may lose its active group in the 

 same way that toxin does and becomes then complementoid. 

 Complement is readily destroyed in blood or serum by 

 heating it to 55° to 56° for half an hour, and is also destroyed 

 spontaneously when serum stands for a day or two, less 

 rapidly at low temperature than at room temperature. 



Amboceptors appear to be specific in the same sense that 

 agglutinins are. That is, if a given cell is used to immunize 

 an animal, the animal's blood will contain amboceptors for 

 the cell used and also for others closely related to it. 

 Immunization with spermatozoa or with epithelial or liver 

 cells gives rise to amboceptors for these cells and also for red 

 blood corpuscles and other body cells. A typhoid bacteri- 

 cidal serum has also some dissolving effect on colon bacilli, 

 etc. Hence a given serum may contain a chief amboceptor 

 and a variety of "coamboceptors," or one amboceptor 

 made up of a number of "partial amboceptors," each specific 

 for its own antigen C'amboceptorogen"). Amboceptors 

 may combine with other substances than antigen and com- 

 plement, as is shown by their union with lecithin and other 

 "lipoids," though these substances seem capable of acting 

 as complement in causing solution of blood corpuscles. 



COMPLEMENTS. 



Students usually have more difficulty with complements 

 and amboceptors than with other phases of the subject of 

 immunity. It may help to look upon complement as an 

 enzyme (or toxin) which does not possess the power of uniting 

 directly with the suhstaiice on which it may act, as other enzymes 

 do. It can be joined to this substance only by means of 

 another and separate chemical. This latter is the ambo- 

 ceptor. It should be apparent that the amboceptor must 

 be capable of uniting with the substance and also with com- 

 plement it must have two uniting groups. Complement 

 must be capable of uniting with amboceptor. It has a 

 uniting group for amboceptor but not for antigen. When 

 through the medium of this separate uniting body it is joined 



