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Incorporation of preparations of mouse interferon in stimulated cultures of normal mouse bone marrow results in a decrease in the number of colonies developing, and in the appearance of unusual cells in colonies. These unusual cells have the granular, vacuolated cytoplasm of the macrophage, but lobed nuclei more typical of cells of the granulocytic series. The evidence suggests that interferon inhibits the normal multiplication and differentiation of mouse granulocyte-macrophage precursors in vitro. [ABSTRACT FROM AUTHOR]

Intravenous or intraperitoneal inoculation of Poly I-Poly C into rabbits induced an inhibitor for rabbit bone marrow colony growth in the serum which associated with interferon after fractionation on Sephadex G-200. Inoculation of hamsters with Poly I-Poly C did not induce either inhibitor for hamster colonies or interferon. Other substances can cause colony inhibition besides interferon and these were detected in both normal rabbit and normal hamster serum. Colony inhibition shows some species specificity, but cross-inhibition of monkey and mouse colony growth was shown with rabbit inhibitor. It is suggested that the basic biological role of interferon may lie in the control of cellular differentiation. [ABSTRACT FROM AUTHOR]

When mice are inoculated with Poly I-Poly C or influenza virus an inhibitor of haemopoietic colony forming cells appears in the serum. The colony inhibiting activity of whole serum is shown to be directly proportional to the interferon titre. Interferon and colony inhibitor are also shown to have the same properties with regard to molecular size and sensitivity to heat, pH and trypsin. [ABSTRACT FROM AUTHOR]

Intraperitoneal inoculation of 100 µg Poly I-Poly C resulted in an eight-fold increase in spleen colony forming cells by the sixth day after inoculation. The same dose of Poly AU resulted in a negligible cellular response and no increase in the level of colony stimulating factor in the serum. The colony stimulating activity of serum after inoculation of Poly I-Poly C was increased, but assay of this increase in early sera was complicated by the presence of a colony inhibitor. Some properties of inhibitor-containing sera were investigated and consideration given to the possibility that the colony inhibitor is related to interferon. [ABSTRACT FROM AUTHOR]

The incorporation of some antigens such as bacterial endotoxin, heterologous erythrocytes and bacterial flagellin preparations can enhance the formation of colonies in cultures of normal mouse bone marrow or foetal liver cells in vitro. Other antigens such as foreign serum proteins and haemocyanin are inactive. This effect depends on the reaction of antigen with a component of normal mouse serum. [ABSTRACT FROM AUTHOR]

The enhancement effect of some antigens on in vitro colony formation by normal mouse bone marrow cells is mediated through a normal serum αmacroglobulin (αM) which is present in newborn animals and shows no immunological specificity. The proportion of antigen and αM affects colony enhancement, and it has also been shown that specific antibody successfully competes with αM for the antigen. It seems likely that antigen-αM complex acts directly on the colony forming cell, rather than indirectly through release of colony stimulating factor. The possible relevance of this phenomenon to immune induction and, to the effect of antigens in promoting irradiation survival is discussed. [ABSTRACT FROM AUTHOR]

It has been shown that intraperitoneal injection of Freund's complete adjuvant can stimulate the multiplication and effect the distribution within the animal of cells which form granulocytic and monocytic colonies in vitro. This response is associated with a leukocytosis and a fall in haematocrit. A variety of antigens were tested all of which resulted in an increase in the number of colony forming cells in the spleen to a greater or lesser degree. Two mechanisms are thought to be involved in this response: (1) with some antigens a direct stimulation of colony forming cells by an antigen-α-macroglobulin complex; and (2) an indirect stimulation of colony forming cells by release of colony stimulating factor from cells other than the colony forming cells. [ABSTRACT FROM AUTHOR]