484 
HEMATOLOGY 
munized with rhesus red cells. Some of the nu- 
merous simian-type blood groups found by us 
have been shown to be analogues of blood groups 
in man. Thus, in chimpanzees, we have found 
analogues of the M-N and Rh-Hr systems, and 
analogues of the M-N system also appear to 
exist in Old World monkeys. 
Cross-immune-type blood groups in primates 
are determined with reagents prepared by im- 
munization of simians with red cells of other 
primate species, including the use of human 
red cells for immunization of simians. The term 
"cross-immune" has been introduced by us to 
stress the special immunological nature of re- 
actions between closely related species, which 
differ from heteroimmune reactions yet do not 
fall into the isoimmune category.*''^ 
METHODOLOGY 
Our investigations of blood groups of apes 
and monkeys resulted from our desire to obtain 
new tools for the study of immunological reac- 
tions and immunogenetics in man. Therefore, in 
our studies on simicns we use the same meth- 
ods that have proved useful for studying the 
blood groups of man. rather than apply tech- 
niques which have been developed for studies of 
blood groups in mice (dexuan method), and 
cattle (test for hemolysis). Other workers who 
had initially used the dextran method for their 
work on monkeys'* have more recently aban- 
doned that method and rallied to our concept.^** 
For testing blood of primates we use the 
classic methods of human blood typing, namely, 
the saline agglutination method, the antiglob- 
ulin test, the agglutination test with red cells 
treated with the proteolytic enzyme ficin, and 
the antiglobulin test with ficinated red cells. 
Moreover, in order to avoid tedious absorptions 
and to obtain reagents of the highest specificity 
we rely primarily on reagents produced by im- 
munization of simians. We scarcely ever use 
sera prepared in rabbits (aside from the stand- 
ard anti-M and anti-N reagents prepared for 
typing human blood), even though rabbit anti- 
sera have given good results in the hands of 
Owen and Anderson and in some of our own 
early work.^^ Other reagents used by us are ex- 
tracts of seeds (so-called lectins) such as Doli- 
chos biflorus (anti-Ai), Ulex europeus (anti-H) 
and Vicia graminea (anti-N), and extracts of 
snails, notably Helix pomatia (anti-A). Lectins 
and snail agglutinins have the advantage of the 
absence of interfering nonspecific agglutinins. 
To avoid pitfalls due to heteroagglutinins, and 
because many of our sera are not yet standard- 
ized and, finally, because the work involves test- 
ing of numerous species, our results are care- 
fully controlled by the following techniques : 
multiple comparative titrations ; 
use of standard panels of red cells ; 
use of reagents of high titers, avidity and 
specificity ; 
multiple testing to prove reproducibility ; 
"blind" reading of the tests to insure ob- 
jectivity. 
These precautions have helped us to avoid 
errors found in some of the earlier and even in 
some more recent reports. It cannot be empha- 
sized too strongly that we never rely on one- 
tube tests and apply the same standards to blood 
typing of simians as are considered essential 
for the application of blood grouping in clini- 
cal and legal medicine. It would be considered 
reprehensible to transfuse blood to a patient or 
offer an opinion in a medicolegal case on the 
base of a single test. This extreme care is nec- 
essary in our laboratory because some of our 
results on primates have been applied for the 
development of clinical procedures such as cross- 
circulation and organ transplantation, while 
other procedures are directly translated from 
experimentation in simians to clinical proce- 
dures in man. To be sure, interesting results 
have been obtained in recent work on rhesus 
blood groups using reagents of minimal titer 
in one-tube tests. "•^'^ However, in our own lab- 
oratory low-titered antisera are considered only 
an indication for further courses of immuniza- 
tion in order to produce more potent reagents. 
RESULTS 
For detailed information on the results ob- 
tained, the readers are directed to our chapters 
in two recent monographs. Here we will 
present in tables I-VIII a schematic summary of 
the most essential findings. 
(1) As recently as 1967,^^ at the convention 
