The MHC is of overwhelming importance in determining the fate of an allograft. Over the past 10 years, our understanding of the serology of this locus, its role in cellular immunity, its biochemistry, and most recently, its molecular biology has increased enormously. Genes for all the known loci, both Class I and Class II, have been cloned and sequenced, and their evolution and function are therefore now more amenable to investigation at the molecular level. Concomitantly, an understanding of the different populations of immune cells involved in the recognition of the antigens encoded by these loci has permitted a more precise immunologic description of the rejection response. It is now clear that recognition of both Class I and Class II allogeneic differences by both helper and cytotoxic T cells has an important role in graft rejection. The goal of transplantation biologists is to take advantage of this increased understanding in order to design new techniques for specifically modifying the immune response to MHC antigens and achieving specific tolerance. Some exciting approaches are already being studied, including specific modifications of both the antigen and the receptor arms of the immune response. It is hoped that these approaches will have new clinical applications in the near future.

Because the nation's health is so greatly influenced by cigarette smoking, this report examines current trends in cigarette advertising and marketing. According to the Federal Trade Commission, total cigarette advertising and promotional expenditures reached $2.1 billion in 1984. From 1974 through 1984, total expenditures increased approximately sevenfold, or threefold after adjustment according to the consumer price index. In 1985, cigarette advertising expenditures accounted for 22.3 percent, 7.1 percent, and 0.8 percent of total advertising expenditures in outdoor media, magazines, and newspapers, respectively. When all products and services were ranked according to national advertising expenditures, cigarettes were first in the outdoor media, second in magazines, and third in newspapers. The proportion of total cigarette advertising and promotional expenditures devoted to promotional activities has increased steadily, from 25.5 percent in 1975 to 47.6 percent in 1984. The proportion of expenditures for cigarettes yielding 15 mg or less of "tar" has increased substantially and has consistently exceeded the domestic market share of these cigarettes. The fastest growing markets are discounted cigarettes and brands containing 25 cigarettes per pack. Several advertising campaigns have targeted women, minorities, and blue-collar workers. The study of these marketing trends should assist health officials in identifying and predicting patterns of cigarette use and in developing health promotion programs that counteract the influence of advertising by incorporating similar, effective techniques.