PLATES 45 ~o 50(Received for publication, January 9, 1963) It is now well established that a number of animal virus diseases (1) as well as plant diseases (2) are directly affected by the genetic makeup of the host. In some cases resistance is dominant; in at least one (mouse hepatitis) susceptibility seems dominant (3). The demonstration that the macrophage is the cell which is paramount in susceptibility to mouse hepatitis virus, MItV, (4) was followed by a demonstration that cultures of newborn mouse liver from susceptible mice yielded susceptible macrophages and from resistant mice yielded resistant cells (3). The susceptibility factor was manifested in the hybrids, F~, and back-cross generations of cultures from young mice as well as in whole mice. It was, therefore, inferred that genetic susceptibility resides in the cells--in particular in the macrophages. In order to test this definitively, four kinds of tests have been carried out directly in the mice and in their cells, and the four methods compared: (a) individual mouse susceptibility (phenotype), (b) production of susceptible offspring (genotype), (c) susceptibility of macrophages from liver cultures, and (d) susceptibility of macrophages from peritoneal washings of adult mice. The first part of this paper reports the results of these correlations, describes the susceptibility of several back-crosses, and confirms the cellular nature of genetic susceptibility to this virus. The second part deals with the susceptibility of peritoneal macrophages in culture and the conversion of resistant to susceptible cells by the addition of extracts of the susceptible cells to cultures of resistant cells (5). If there is a correlation between the susceptibility of macrophages and the susceptibility'of the individual animal to MHV infection, then different kinds of cross and back-cross generations of susceptible and resistant animals can be studied by examining their macrophages without sacrificing the mouse, and the progeny can be used for selective breeding.
PATHOLOGY: KANTOCH AND BANG 1553 in embryos. Results of the present experiments also obviously imply that a subcellular factor exists in the blood of patients with neoplastic disease that is involved in the high rate of chick embryo mortality. There is, however, no basis at present for suggesting that a virus is implicated in these phenomena. The utilization of these techniques, as reported herein, further suggests a possible tool for clinical diagnosis. Experimental data at hand from experiments in progress are insufficient to make a complete analysis possible. Summary.-Whole blood and blood fractions from patients and animals with neoplastic disease produced a high rate of mortality of chick embryos when inoculated onto the chlorioallantoic membrane. Blood and blood fractions from normal and non-neoplastic sources caused little toxicity and only a low percentage of deaths of the chick embryos. Expanded studies are underway. The authors wish to express their appreciation to Miss Jo-Anne Hurt for technical assistance.
A high per cent of false positive results for rubella virus IgM antibodies determined by immune fluorescence were detected in sera of pregnant women. After absorption with Staphylococcus suspension, Cowan 1 strain, and aggregates of human immunoglobulins, the false positive reactions due to IgM antiimmunoglobulin were eliminated.
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