30 MASS. EXPERIMENT STATION BULLETIN 370 



Rothe Meyer, Engelbreth-Holm, and Uhl (174) report that the immunity 

 of chickens naturally resistant, or the immunity of birds following spontaneous 

 recovery, protects the birds not only from the strain with which they were in- 

 oculated, but also from other strains of the leukosis agent as well (this included 

 their Strain E-S). In this connection it is of interest that Stubbs and Furth (195) 

 found that most chickens which were immune to their Strain 1 were also resistant 

 to Strain 2, but not to Strain 13. Oberling and Guerin (148) inoculated sarcoma 

 material (the sarcoma induced by their strain of leukosis agent) into the breast 

 muscle of 15 chickens which had been refractory to a previous inoculation with 

 the leukosis agent. A small nodule, which later regressed, developed at the site 

 of injection in only one chicken. Eight of these birds were later successfully 

 inoculated with material from an unrelated transmissible chicken tumor similar 

 to the Rous sarcoma. 



The blood plasma of spontaneously recovered chickens was demonstrated 

 to have a relative neutralizing effect on the agent contained in leukotic blood 

 plasma, but none on leukemic whole blood (Furth 76, and Rothe Meyer and 

 Engelbreth-Holm 173). Exposure to a temperature of 52° C. for 30 minutes did 

 not destroy the inhibiting action of plasma from a spontaneously recovered 

 chicken (Rothe Meyer and Engelbreth-Holm, 173). The relative nature of such 

 a neutralization effect was indicated by Furth's experiments. He (76) found that 

 7 out of 27 chickens developed the disease when inoculated with a mixture of 

 leukotic plasma and plasma from birds chat had recovered from the disease. 

 In another experiment 6 out of 15 fowls developed leukosis after inoculation with 

 a similar mixture using normal blood plasma instead of thac obtained from 

 recovered birds. The exposure of serum and agent was limited to 20 minutes in 

 the above experiments. When this exposure time was lengthened to an hour at 

 37.5° C. complete protection was obtained in eight birds receiving a mixture of 

 neutralizing serum and cell-free agent. Rothe Meyer, Engelbreth-Holm and Uhl 

 (174) found chat the plasma of a chicken with chronic erythroblascic anemia 

 (a chronic form of erythroblastic leukosis) was also capable of neutralizing the 

 cell-free agent. This characteristic was not manifest by the plasma from a case 

 of acute leukosis, (the leukosis agent in the piasma of these diseased birds was 

 destro^-ed by heating to 55° C. for a half hour). These workers also report that 

 the plasma of a chicken recovered from their pure strain of erythroblastic leukosis 

 would neutralize the agent of their complex strain E-S as well. 



Uhl, Engelbreth-Holm, and Rothe Meyer (205) demonstrated a neutralizing 

 action on the agent of leukosis by the serum of ducks which had received multiple 

 injections of leukotic chicken blood. They were able to completely neutralize 

 the agent present in cell-free leukotic plasma with the serum of such ducks and 

 to inhibit the action of the agent in whole leukotic blood. Serum from normal 

 untreated ducks or those which had received injections of normal chicken blood 

 was devoid of this power. The neutralization tests were conducted in vitro at 

 a temperature of 37° C. for two hours. Greppin (91) found a slight neutralizing 

 action in the acetone extract of the serum of ducks which had received washed 

 leukosis corpuscles. He also found a slight neutralizing effect with the serum 

 obtained from rabbits treated with bone marrow of a leukotic chicken. 



Attempts have been made to convey passive immunity to chickens with serum 

 of a spontaneously recovered chicken, but without success (Jarmai, Stenszky, 

 and Farkas 105, Wallbach 213). 



The subcutaneous and intramuscular injection of leukotic material into chick- 

 ens has not produced a significant degree of active immunity (Jarmai, Stenszky, 

 and Farkas 105, Engelbreth-Holm 47, and Ellermann 40). Oberling and Guerin 



