The principal long-term goal of this research is to determine the molecular genetic basis of human immune responsiveness to allergens. Atopic allergy will provide a particularly good model for our studies, since the doses of most inhaled allergens are very low and immunologically limiting. We will study two aspects of the immunogen-etic control: the determination of specific immune responsiveness by HLA-D and TcR genes; the regulation of overall IgE antibody production, which we postulate to be controlled by genes encoding certain lympho-kines, lymphokine receptors and/or proteins which bind to the lymphokine gene promoters or enhancers. We will investigate the relationship between the DNA sequences of HLA-D- region genes and specific IgE and IgG antibody responses toward several ultra-pure allergens, focusing on responsiveness to minor ragweed allergens, Amb V and Amb VI, where single major epitopes are recognized by specific Class II molecules. HLA-D associations to further allergens will be investigated primarily as part of an international HLA and Allergy study. Experiments will involve antigen-specific human T-cell clones and lines, including quantitation of lymphokine production and analysis and sequencing of T-cell receptor (TcR) genes. Based on TcR sequence similarities in the T-cell clones, we will design specific oligonucleotides to investigate the relationships of specific TcR gene sequences to responsiveness or non-responsiveness to Amb V and Amb VI. We will analyze the genetics of overall IgE responsiveness in 42 large nuclear families and several selected extended pedigrees from these and further families. We will define a new atopy-associated phenotype, which is based on a subject's ability to respond to a defined set of inhalant allergens. We will investigate the distribution of this phenotype in population studies and its mode of inheritance by segregation analysis in the families. We will investigate linkage between the defined, novel IgE Ab phenotype and polymorphic genetic markers in (or near) certain key lymphokine and lymphokine receptor genes that are known to be important in IgE regulation in vitro. Genetic studies will be coordinated with cellular immunologic studies that are designed to explore the molecular basis of IgE regulation. A unique asset for our studies is the availability of extensive epidemiologic and laboratory computerized data, and multiple serum samples and cells from two large populations of ca 500 and ca 400 subjects. Furthermore, we will be analyzing 1000+ atopic subjects from a unique international HLA and Allergy study, which is part of the 1991 Histocompatibility Testing Workshop. We also have data and sera on 55 large families from the first two groups of subjects, and will collect further epidemiologic data and leukocyte samples from these and other families and extended pedigrees for genetic studies under this grant.