The most remarkable feature of the immune response is its ability to generate cells and antibodies specifically reactive with an enormous variety of foreign antigens while normally avoiding the production of autoreactive elements. An accumulating body of data demonstrates that a distinct lineage of B cells (1), the Ly-1 + B cell subset, does not display this feature, but rather is associated with the production ofautoreactive antibodies (2). We are unaware of autoimmune pathology directly demonstrated to be the result of an Ly-1 + B cell-Ig product; however, Ly-1+ B cell frequency is elevated in some autoimmune strains of mice (3). In addition to their association with autoreactive antibody, Ly-1 + B cells have been shown to have unique growth potential (1, 4); to produce most of the serum IgM found in normal, unimmunized animals (4); and the Ig repertoire of the subset may be restricted (4, 5). These findings imply that this subset has a role in normal physiology, and perhaps autoimmune pathology. A B cell subset has been identified in humans that bears the homologous marker Leu-1/T1 (CD5) (6). A similar functional role for CD5+ B cells in man has been proposed (7); human CD5+ B cells have been shown to produce autoreactive antibody (8, 9) and to be present at elevated frequency in rheumatoid arthritis (10).Normal mice produce antibodies that are reactive with protease-treated autologous erythrocytes (BrMRBC) 1 (11) ; cells producing such antibodies are present in unimmunized mice at very high frequencies, as first demonstrated by Cunningham (12) . We and others (13)(14)(15) have shown that at least some anti-BrMRBC plaqueforming cells (PFC) recognize the polar headgroup of the common membrane phospholipid, phosphatidyl choline (PtC). Most splenic anti-BrMRBC PFC have been

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Summary The smoking habits of a group of pregnant women have been recorded and related to the level of carboxyhaemoglobin (COHb) in the circulating blood. Simultaneous maternal and fetal COHb levels at delivery were estimated and on average the fetal levels were 1.8 times greater than the related maternal level. Samples of fetal blood were exposed to carbon monoxide in vitro and an appreciable shift to the left of the haemoglobin dissociation curve was demonstrated. Cigarette smoking during pregnancy diminishes the oxygen carrying capacity of both fetal and maternal blood, affects maternal oxygenation by increased pulmonary venous admixture and diminishes the oxygen available to the fetus at the tissue level by its effect on fetal oxyhaemoglobin dissociation.

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Summary.-Monoclonal antibodies to epithelial -cell antigenic determinants, labelled with 1231 and 1251, were administered parenterally to immunodeficient mice bearing human tumours derived from a human cancer cell line. Anterior, posterior and lateral radioscans of the body were taken with a gamma scintillation camera at various times from immediately to 65 days after injection. Visual displays of the images were processed by standard computer techniques. The model used a human colon-cancer cell line, HT29, and the monoclonal antibody, AUA1, which is specific to an epithelial proliferating antigen. Tumour detection was achieved in all the mice. The smallest tumour detectable appeared to be about 1 mm in diameter. The degree of antibody uptake in a tumour depended on its size and the blood supply of its surrounding tissues We believe that the technology and skills are now available for accurate radioimmunodetection of cancer in man.

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