Effect of Friend leukemogenic virus on antibody forming ceils to a bacterial somatic antigen

SUMMARY-Adult BALB/c mice were infected with Friend leukemogenic virus (FLV) and tested for their ability to produce speciAc antibody-secreting cells to Escherichia coli after challenge immunization. A direct bacteriolytic plaque assay with viable E. coli as the indicator was used for the assay. Normal noninfected animals had a vigorous immune response after immunization with the lipopolysaccharide antigen derived from the bacteria. Mice infected with virus also responded with plaque-forming cells (PFC) to E. coli, but the magnitude of the response was markedly depressed. The time of virus infection relative to the day of immunization was an important factor, since the greatest suppression occurred in animals infected 3, 7, or 14 days before immunization. There was no signiAcant suppression, and occasionally an enhancement, when mice were infected with virus 1 or 2 days after immunization. In general, the greatest depression was apparent, regardless of the day of immunization or infection, when the number of PFC was calculated per million leukocytes rather than per whole spleen. Seru