CHAPTER LXXI 



THE USE OF HUMAN SERUM FROM CONVALESCENT CASES 

 IN PREVENTION AND TREATMENT 



WILLIAM H. PARK 



Bureau of Laboratories, Department of Health, City of New York 



It is now well known that persons who recover from any one of a number of the 

 infectious diseases develop antibodies which accumulate in the blood. In at least 

 several of these diseases the accumulation is great enough in the blood to transfer 

 through injections of a few cubic centimeters a considerable immunity to others and 

 possibly to transmit sufficient to be used therapeutically. 



The advantages of human antibodies over those of the horse or any other animal 

 are several. Since they are used to confer immunity in a member of the same species 

 they persist longer. Thus, a guinea pig receiving ten units of diphtheria antitoxin 

 prepared in an immunized guinea pig remains immune for from six to eight months, 

 while a guinea pig receiving ten units of antitoxin made in an immunized horse re- 

 mains immune for only two or three weeks. The disadvantages are several. The 

 potency of the serum in the antibacterial or antitoxic antibodies from convalescent 

 cases is very variable, is often low, and is usually unknown, the amount of serum 

 being frequently so small and the need for its immediate use so great that tests are 

 not made. There is the great difficulty also of getting a supply at the time needed, 

 for it is impossible to count in an emergency on a donor who has recently had the 

 disease. The greatest concentration of the antibodies in the serum is usually one or 

 two weeks after the recovery. There is then a gradual decline. Many persons after re- 

 covery retain appreciable amounts for a lifetime. Because of the drawbacks, con- 

 valescent serum is rarely used when there is available a horse serum of much greater 

 antibody potency. The serum can be stored for months because the antibodies are 

 fairly stable. 



The serum from many persons who have never had certain communicable diseases 

 possesses antibodies against the micro-organisms causing these diseases. Thus we 

 know that many persons who have never had diphtheria are not only immune to 

 diphtheria, but that in the blood they have appreciable concentrations of diphtheria 

 antitoxin. We know that the same is true as to scarlet fever antitoxin and anti- 

 bacterial antibodies in many who have never had scarlet fever. People who have 

 never had pneumonia frequently have very considerable quantities of antibodies 

 against one or the other of the different pneumococcus types. The same is true for 

 poliomyelitis and many other infections. Our only explanation is that these persons 

 at some time had a very light, unrecognized sickness or that they were for a time 

 healthy carriers of micro-organisms. It is important to remember this fact; otherwise 

 we may make misleading conclusions, as, for instance, when the convalescent serum 

 from a case of epidemic encephalitis neutralizes the virus of poliomyelitis the probabil- 



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