254 
malaria 
neutralizing with NaOH. A positive test 
was obtained in 29 instances using the sera 
from 34 patients showing circulating para¬ 
sites. However, the use of antigens pre¬ 
pared in the same manner in different 
areas, did not furnish such promising re¬ 
sults. Repeated, unsuccessful efforts have 
been made in this laboratory to demonstrate 
a specific precipitin reaction in avian and 
monkey malaria. Antigens prepared from 
practically pure concentrations of P. 
knowlesi parasites and known to have a 
high antigenic potency for the malarial 
complement-fixing antibodies failed to pre¬ 
cipitate antibodies in the serum of animals 
obtained during the various stages of the 
acute and chronic infection or even with 
hyperimmunized serum. From the studies 
on humoral immunity in malaria it seems 
highly probable that there should be spe¬ 
cific precipitins at some stage of the infec¬ 
tions and that the failure of consistent 
demonstration is due to low concentrations 
of the antibodies and a weakly reactive 
antigen. 
Summary 
Humoral immune substances in the form 
of specific antibodies have been conclusively 
demonstrated in malarial infections of 
birds, monkeys and man. Those identified 
thus far are protective antibodies, agglu¬ 
tinins, and complement-fixing antibodies. 
There is also suggestive evidence for pre¬ 
cipitins, although their specificity is in 
doubt and they cannot be demonstrated 
consistently. The development of immun¬ 
ity to malaria can be shown to accompany 
the formation of the specific antibodies. 
Although not definitely proved, there is 
much inferential evidence pointing to the 
specificity of the immune response in 
malarial infections as being the concern of 
humoral immune bodies. 
