The purpose of this study was to determine if polymerase chain reaction (PCR) could be used to detect FeLV proviral DNA in bone marrow samples of cats with varying suspicion of latent infection. Blood and bone marrow samples from 50 cats and bone marrow from one fetus were collected, including 16 cats with diseases suspected to be FeLV-associated. Serum enzyme-linked immunosorbent assay (ELISA), blood and bone marrow immunofluorescent antibody test (IFA), and blood and bone marrow PCR were performed on each cat, and IFA and PCR on bone marrow of the fetus. Forty-one cats were FeLV negative. Five cats and one fetus were persistently infected with FeLV. Four cats had discordant test results. No cats were positive on bone marrow PCR only. It appears persistent or latent FeLV infection is not always present in conditions classically associated with FeLV.

The concept of nonspecific cellular defense of the respiratory system of poultry against respiratory pathogens by "preventive activation" of avian respiratory phagocytes (ARPs) was tested in an in vivo protection trial. Chickens were stimulated intratracheally by Pasteurella multocida Choloral vaccine strain. Seven hours later, these and mock-inoculated control chickens were challenged with pathogenic Escherichia coli via the air-sac route. Stimulated chickens had a 25-fold-elevated number of ARPs compared with mock-inoculated control chickens. The proportion of active phagocytes and the phagocytic capacity of these cells was higher in the ARP populations of stimulated chickens than in the ARP populations of control chickens. In vivo protection against E. coli air-sac infection was demonstrated by reduction of morbidity and mortality rates, diminished weight loss, and lower scores of gross and histopathological lesions of P. multocida-stimulated chickens compared with mock-inoculated controls.

Ducks were inoculated parenterally, up to 4 times, with bovine serum albumin (BSA), B gamma globulin (BGG), or horse gamma globulin (HGG). Their sera were tested in immunodiffusion tests for precipitins. Only BSA and BGG induced precipitins. Only 7 of 443 sera tested, obtained from 3 of 62 inoculated ducks, developed a precipitin line with homologous antigen. All 7 sera were obtained from the earliest bleeding (7 days) after inoculation. Sera were also tested for agglutinins in direct passive hemagglutination (DPHA) and direct red-cell-linked antigen tests (DRCLAT) and for nonagglutinating antibodies in indirect red-cell-linked antigen tests (IRCLAT). No duck had a passive-hemagglutination-demonstrable primary immune response. Demonstrable DPHA titers after subsequent inoculations were very low compared with responses to these antigens of other species noted by other workers. Duck immune response was greatly diversified: all inoculation regimens that induced agglutinins in some ducks left others completely unstimulated. Precipitins and agglutinins of the same ducks correlated well: those 7 sera that had precipitins also had the highest DPHA titers for the 3 donor ducks. However, hemagglutinating titer and presence of precipitins in sera of different ducks correlated poorly. Increasing the age of the ducks at the first inoculation from 6 to 10 weeks increased the number of responders and DPHA titers of their sera. Non-agglutinating antibodies were demonstrated in anti-BSA sera: in IRCLAT, the sera had titers 2-to-256-fold higher than the sera in DPHA or DRCLAT had. Duck immunoglobulins were deficient in those immunological reactions (precipitation and agglutination) that require functional bivalency.

Young ducklings were inoculated intravenously (IV) twice with either chicken or sheep red blood cells (CRBC, SRBC). Breeder ducks were inoculated IV twice with an increased dose of CRBC. Sera of these actively immunized ducks and sera of day-old ducklings from the CRBC-inoculated breeder ducks were tested for hemagglutinins in direct-hemagglutination (DHA) tests. The young ducklings and the breeders responded with very low DHA titers to CRBC and SRBC. Although ducklings inoculated with CRBC developed a true secondary response to a second CRBC inoculation, ducklings inoculated with SRBC failed to develop elevated titers after a second of SRBC inoculation. Half the breeders failed to develop higher titers to a second CRBC inoculation. Sera from the majority of day-old ducklings hatched from eggs laid after one inoculation of the breeders had no or only minimal DHA activity. Sera of ducklings hatched from eggs laid after the second inoculation had somewhat higher DHA titers, and in greater proportion. Still, many of those duckling sera had no or minimal DHA titers. Results with Sephadex G-200 fractions indicated that hemagglutinins after one inoculation resided primarily in duck immunoglobulin M (DIgM). Sera of ducks inoculated twice with CRBC had hemagglutinating activity in DIgG, too. Hemagglutinating activity was demonstrated in both 2-mercaptoethanol-sensitive (DIgM) and -resistant (DIgG) antibodies. The conspicuously low titers in all DHA-positive sera agree with results of previous studies, suggesting that DIg's are deficient in immunological reactions requiring functional bivalency.