In an interesting paper Campbell (1936), while welcoming the studies that were being concentrated on improving maternity care, drew attention to what he called "a more subtle and sinister condition", the "excessive smoking" which, during the previous two decades, had "clutched the young women of this country (America) in a manner resembling the invasion of an epidemic working in virgin soil". His paper, which was based on the conviction of his own observations, included his review of the literature and in particular a review of such experimental work as there was on the effect of nicotine or tobacco extracts. Campbell had also asked the members of the American Association of Obstetricians and Gynaecologists for their opinion about the effect of smoking 25 cigarettes or more daily on maternal health and he quoted some of the interesting replies he received, the great majority of which supported his beliefs that excessive smoking in pregnancy was harmful to the mother. There was no suggestion in his paper that smoking might also have an effect on the foetus.Since then smoking in pregnancy has received spasmodic attention. A few workers have presented evidence to suggest that smoking may prevent a successful outcome to the pregnancy (Frazier, Davis, Goldstein, and Goldberg, 1961;Zabriskie, 1963;Butler, 1965;Russell, Taylor, and Maddison, 1966;Steele and Langworth, 1966)

Interleukin-4 (IL-4) regulates multiple stages of the antigen-dependent phase of B-cell development. However, its precise role in regulating B lymphopoiesis in bone marrow is not as well defined. We examined whether surface IgM- normal and leukemic human B-cell precursors (BCP) expressed IL-4 receptors using biotinylated IL-4. Constitutive expression of IL-4 receptors was detected on both normal and leukemic BCP. A higher percentage of normal BCP (82% +/- 15%) expressed IL-4 receptors compared with leukemic BCP (44% +/- 8%). Using mean fluorescent intensity as an indicator of receptor level on the IL-4 receptor positive cells, normal (91 +/- 41) and leukemic (44 +/- 37) BCP expressed comparable numbers of receptors. IL-4 induced the expression of CD23 on 30% of the leukemic BCP cases examined. IL-4 induced CD23 on surface IgM+ fetal bone marrow lymphoid cells but not on the surface IgM- normal BCP, despite the presence of detectable receptors on the surface IgM- cells. IL-4 did not stimulate proliferation of normal BCP, nor could it enhance the effect of recombinant IL-7 or low molecular weight B-cell growth factor. However, IL-4 increased the expression of surface IgM and surface Ig kappa on in vitro differentiated pre-B cells. Our collective results identify no role for IL-4 in the proliferation of normal or leukemic BCP, but identify a role in the enhancement of surface Ig expression during pre- B to B-cell differentiation.

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