The effect of antiserum on the interferon (IF) production in macrophages by Newcastle disease virus (NDV) has been studied. Completely neutralized NDV lost its IF-inducing ability, but under-neutralized NDV revealed an enhanced IFinducing capability. This enhancement of IF production by unneutralized NDV was also observed in antiserum-treated cells. Enhancement phenomena appeared to be based on immunological specificity. Under-neutralized NDV was also adsorbed more rapidly and at a higher rate to normal cells than unneutralized NDV. Unneutralized NDV also adsorbed more efficiently to antiserum-treated cells and to cells derived from immunized mice than to normal cells. The significance of these phenomena is discussed in relation to the induction mechanism of IF in macrophages.
In vitro interferon (IF) production in peritoneal macrophages of normal and Newcastle disease virus (NDV)-immunized mice was studied. Of ascites cells used, 80% were macrophages, 14% lymphocytes, and 6% polymorphonuclear leukocytes. It was indicated that IF was produced mainly in the macrophages after NDV inoculation. IF production in the macrophages derived from immunized mice was more enhanced than that in those from normal mice. It is not clear at present, however, whether this enhancement is based on immunological specificity. The IF production in the culture of macrophages reached its maximum value in 6 to 9 hr after inoculation of the inducer. After 12 hr, the IF titer in the culture fluid decreased gradually. A possible explanation of this fact is that there may be partial inactivation of IF by some cellular components.
When Newcastle disease virus (NDV) was inoculated into macrophage cultures, interferon (IF) of various molecular weights appeared in the culture fluid. The molecular weight of IF produced in the macrophages derived from normal mice in at least 6 hr post‐inoculation of inducer was different from that produced in the macrophages from immunized mice. The IF with a molecular weight as high as 100 000 was unstable against pH 2 treatment and heat treatment, while that of 70 000 or less was stable.
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