In recent years rapid progress has been made in the areas of T cell and B cell biology, cell-cell and cell-matrix/stroma interactions. The use of isolated subunits of the T cell receptor invariant chains has been instrumental in defining their role in signal transduction and tyrosine phosphorylation. A role of src family phosphotyrosine kinases in T cell activation has been demonstrated and several phosphotyrosine kinase substrates have been identified and their functions characterized. Homologous recombinant techniques have led to the development of murine strains that lack CD4 or CD8 expression. These models are likely to be instrumental in studying the role of T cell subsets in autoimmune disorders, tissue transplant rejection and tumor rejection. A role of major histocompatibility complex I in the development of T cell subsets and NK cells has been defined. Recent data suggest a role of interaction between plasma membrane molecules of activated T helper cells and B cells, B cells primed with plasma membrane of activated T helper cells and cytokines, and interaction between bone marrow stromal cells and B cell progenitors and precursors, in the B cell development, proliferation, and differentiation. The structure and functions of adhesion molecules, especially with regard to signal transduction and homing events, are better defined.

Section I: T Cell Receptors and T Cell Activation.- T Cell Receptor Structure and Function: Analysis by Expression of Portions of Isolated Subunits.- The T Cell Antigen Receptor Tyrosine Kinase Pathway.- Dissection of the Hb(64-76) Determinant Reveals That the T Cell Receptor May Have the Capacity to Differentially Signal.- CD28 Receptor Crosslinking Induces Tyrosine Phosphorylation of PLC?1.- Structure and Function of CD45: A Leukocyte-Specific Protein Tyrosine Phosphatase.- Multidrug Resistant Gene 1 Product in Human T Cell Subsets: Role of Protein Kinase C Isoforms and Regulation by Cyclosporin A.- Integrins, ?? T Cells, and Autoimmunity.- The Interleukin-2 Receptor: A Target for Immunotherapy.- Section II: T Cell Development.- Lymphocyte Development in Mice Deficient for MHC Class I Expression.- Generation of Mutant Mice Lacking Surface Expression of CD4 or CD8 Gene Targeting.- Alteration of T Cell Lineage Commitment by Expression of a Hybrid CD8/CD4 Transgene.- Differential Involvement of Protein Tyrosine Kinases p56lck and p59fyn in T Cell Development.- Mechanism of Tolerance Induction.- Section III: B Cell Development, Activation, Proliferation, And Differentiation.- B-Lymphocyte Lineage-Committed, IL-7 and Stroma Cell-Reactive Progenitors and Precursors, and Their Differentiation to B Cells.- Regulatory Cells and Cytokines Involved in Primary B Lymphocyte Production.- The Role of IL-7 and Its Receptor in B-Cell Ontogeny.- Role of Contact and Soluble Factors in the Growth and Differentiation of B Cells by Helper T Cell.- B-Cell Activation Mediated by Interactions with Membranes from Helper T Cells.- The Low Affinity IgE Fc Receptor (CD23) Participates in B Cell Activation.- Section IV: Adhesion Molecules: Structure, Regulation and Functions.- T Cell AdhesionCascades: General Considerations and Illustration with CD31.- Analyses of VLA-4 Structure and Function.- On the Regulation of ?2 Integrins.- Leukocyte-Endothelial Cell Adhesion as an Active, Multi-Step Process: A Combinatorial Mechanism for Specificity and Diversity in Leukocyte Targeting.- Contributors.