[Investigations into the relationship of cell susceptibility and antibody formation and its importance in the pathogenesis of avian leukosis].

Crossbred progeny from matings of Leghorn males (lines M and G), predominantly susceptible to leukosis infection, and females from a predominantly leukosis-resistant line (line R) showed a high incidence of mortality from spontaneous leukosis. Immunological tests revealed that this field infection was caused by a subgroup A leukosis virus. Tests for susceptibility to infection and presence of RSV antibodies in embryos and pullets respectively of lines R, G and M yielded the following results: line R appears to be predominantly resistant to BH-RSV (RAV1) and BH-RSV (RAV2) (subgroups A and B), line G predominantly resistant to BH-RSV (RAV2) (subgroup B), but susceptible to BH-RSV (RAV1 ) (subgroup A), while line M is predominantly susceptible to both BH-RSV (RAV1 ) and BH-RSV (RAV2) (subgroups A and B). Resistance to infection and formation of antibodies are closely interrelated. Resistant chickens are generally free of antibodies specific to antigens of the particular subgroup. Hens resistant to infections from a certain subgroup of leukosis viruses are unable to produce antibodies against this antigen and therefore cannot protect their progeny by giving them sufficient maternal antibody. Matings of such resistant hens with males homozygous dominant susceptible to leukosis infections will produce progeny which are not only susceptible to leukosis infections but which also lack maternal antibodies to protect them against leukosis viruses during the particularly critical first few days of life.