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Addition of low concentrations of the synthetic double-stranded polynucleotides Poly I-Poly C and Poly AU to stimulated cultures of normal mouse bone marrow increased the number of macrophage colonies in the cultures. Double strandedness of the polynucleotides was essential for activity and they were active without the s-globulin which was previously shown to be a necessary co-factor in colony potentiation by some antigens. The evidence suggested that polynucleotides acted at the cell surface to make colony forming cells more responsive to colony stimulating factor. [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]

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]

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]