No abstract

The ability of the JHM3 strain of mouse hepatitis virus (MHV) to induce natural killer (NK) cells was examined. Infection of C57BL/6 (B6) mice with this virus resulted in the augmentation of natural cytotoxicity against YAC-I target cells in the absence of a detectable interferon response. The cells responsible for this increased cytotoxicity were sensitive to complement-mediated lysis with an anti-Q-5 reagent but not with a Thy 1.2 antiserum, indicating that they possess an NK-like surface phenotype. Although variation in the NK response of individual B6 mice following JHM virus infection was found, even the animal with the most responsive NK cell population had no detectable interferon in the spleen. This finding contrasted with observations with an unrelated virus (lymphocytic choriomeningitis virus) and a serologically related strain of MHV. Infection with both of these viruses induced augmented NK cell activity and interferon responses. In addition, we found that neither the ability to mount an augmented NK cell response nor preferential lysis of virus-infected targets correlated with resistance or susceptibility to JHM virus infection.

Human, animal, proprietary, and soy milks are comparable to human serum C5 in opsonization of baker's yeast. Bovine milk and human serum opsonically reconstitute C5-deficient mouse serum. Such reconstitution is selectively inhibited by antiserum to human C5. Further characterization suggests that bovine milk contains material structurally and functionally similar, but not identical, to human C5.

Maximum opsonization of baker's yeast particles by normal human serum requires C5. Sera from mice genetically lacking C5 are deficient in yeast opsonic activity but can be restored to normal by addition of highly purified human C5. Human, animal, proprietary and soy milks are comparable to human C5 in opsonic reconstitution of C5-deficient mouse serum. This reconstitution by each milk is inhibited by highly purified anti-human C5. Further characterization of the opsonically active principle(s) in milk has been carried out by comparison of bovine milk with human C5 in the following assays: 1) effective molecular titration of hemolytically active C5 in plasma or milk by lysis of EAC14oxy23 cells in the presence of C6-9; 2) generation of chemotactic activities by addition of endotoxin or antigen-antibody complexes; 3) heat stability of opsonic activity; 4) inhibition of opsonic reconstitution by milk or plasma of C5-deficient mouse serum by addition of highly purified anti-C5, anti-C3, or anti-immunoglobulins; and 5) chromatographic separation.