Table 8 . - - Agglutination of human eryt±irocytes by fresh skipjack serums 

 Cells Serums, diluted 1:4 



10^' 2 11^ 12^ 13^ 14-^ IS^'^^lb^ 17^ 18^ 



Type A 

 Type B 

 Type O 



the Oregon coast by E . K . Holmberg on the 

 tuna troller Scarab. This observation suggests 

 at least the possibility of interspecific differ- 

 ences with respect to the occurrence of natural 

 agglutinins in bloods of some species of tuna. 

 (Alternative explanations such as seasonal vari- 

 ations in antibody titer and parasitic infestations 

 are of course possible. These problems are 

 currently being studied in this laboratory with 

 the assistance of George Durall, using as a 

 model an isoantibody system discovered this 

 year in a local population of catfish (manuscript 

 in preparation) . 



Human "type-A" substance in frozen 

 tuna blood. Studies conducted at Santa Barbara 

 with the assistance of Barbara Drake and Lucian 

 Sprague have supplied evidence of a substance 

 in tuna blood resembling the human A blood type 

 antigen. Table 9 shows the results of a series 

 of slide agglutination tests that give evidence of 

 a specific inhibition of human anti-A typing 

 serum by the centrifuged (5, 000 r.p.m. for 20 

 minutes) whole bloods of yellowfin mnas . All 

 tests were performed by mixing 1 drop of fro- 

 zen tuna blood, previously diluted 1 in 4 with 

 1 percent saline solution, with 1 drop of serum 

 dilution. Cells were added to this mixture after 

 it had stood for 15 minutes at room temperature. 

 Readings were made 15 minutes after this step. 

 It will be noted that some of the tuna bloods 

 contain natural agglutinins for human B cells 

 but that only one (fish 204) is capable of agglu- 

 tinating human A cells as well. One fish, 209, 

 appears to lack A inhibitor, but whether this i s 



indicative of individual lack of A antigen is not 

 known. 



The experiments recorded in table 10 

 show that blocking" ("incomplete, " "inhibiting ) 

 antibodies in tuna blood are not the cause of the 

 inhibition noted, for the absorption of tuna blood 

 with human A cells did not reduce the inhibiting 

 factor . Here the blood of a single tuna (207) 

 was diluted 1 in 4 with 1 percent saline and ab- 

 sorbed with human cells . A drop of absorbed 

 blood was placed on a slide with a drop of ser- 

 um dilution and allowed to stand for 15 minutes 

 after which time a drop of cell suspension was 

 added. Agglutinations were read after 15 min- 

 utes. The erythrocytes were washed in 1 

 percent saline solution after being used for 

 absorption and were then tested with typing 

 serums to see if any A antigen had been ab- 

 sorbed by them . Negative results were 

 obtained in these tests. 



The inhibition was found to be partially 

 associated with material that failed to pass 

 through a Sweeny bacterial syringe filter. This 

 material was presumably fragments of stroma. 

 This presumption is supported by observations 

 that washed stroma causes specific inhibition 

 and also specifically absorbs anti-A from a 

 mixture of anti-A and anti-B serums. (These 

 last two observations are of a preliminary 

 nature in that the relatively low titers of in 

 hibitor and available antiserums made it 

 difficult to obtain markedly contrasting prepara- 

 tions) . 



10 



