T cells also originate in the bone marrow, but all the important events in their development occur in the thymus

Many autoantigens are not so abundantly expressed that they induce clonal deletion or anergy but are not so rare as to escape recognition entirely HIV infection leads to low levels of CD4 T cells, increased susceptibility to opportunistic infection, and eventually to death T cells are specialized to recognize foreign antigens as peptide fragments bound to proteins of the major histocompatibility complex Dominant immune suppression can be demonstrated in models of tolerance and can affect the course of autoimmune disease The 9th edition also includes updates on recent developments in multiple immunology subfields. Notably, the section on innate immunity has added a discussion of immune effector modules, which are critical to understanding the pathogenesis of inflammatory bowel disease, intestinal infection, and several other diseases. The section on therapeutics now contains a discussion of chimeric antigen receptors, an active and important area of cancer immunotherapy research. A particularly significant feature of this edition is an overhaul of the end-of-chapter questions and the addition of an instructors’ question bank. The 9th edition replaces the handful of often open-ended review questions at the end of each chapter with multiple-choice and true-false questions, providing an easier avenue for instructors to test the material.Germinal center B cells undergo V-region somatic hypermutation and cells with mutations that improve affinity for antigen are selected Activated CD8 T cells and some CD4 effector T cells express Fas ligand, which can also activate apoptosis NK cells possess receptors for self molecules that inhibit their activation against uninfected host cells Autoantibodies against extracellular antigens cause inflammatory injury by mechanisms akin to type II and type III hypersensitivity reactions Innocuous antigens can cause type II hypersensitivity reactions in susceptible individuals by binding to the surfaces of circulating blood cells

That these antibodies might have a crucial role in immunity was reinforced by Jules Bordet’s discovery in 1899 of complement, a component of serum that acts in conjunction with antibodies to destroy pathogenic bacteria.Paul Ehrlich advanced the development of an antiserum as a treatment for diphtheria and developed methods to standardize therapeutic serums. An important question is whether vaccination can be used therapeutically to control existing chronic infections

T-cell α-chain genes undergo successive rearrangements until positive selection or cell death intervenes Immature B cells that bind self antigens undergo further receptor rearrangement, or die, or are inactivated

Contents

The nonspecific responses of innate immunity are necessary for an adaptive immune response to be initiated Some peptides and lipids generated in the endocytic pathway can be bound by MHC class I-like molecules that are encoded outside the MHC Lymphocyte migration, activation, and effector function depend on cell-cell interactions mediated by cell-adhesion molecules Modulation of the immune system might be used to inhibit immunopathological responses to infectious agents

B-cell responses to bacterial antigens with intrinsic ability to activate B cells do not require T-cell help Cytotoxic effector proteins that trigger apoptosis are contained in the granules of CD8 cytotoxic T cells Phagocyte ingestion of complement-tagged pathogens is mediated by receptors for the bound complement proteins Activation of specialized antigen-presenting cells is a necessary first step for induction of adaptive immunity

Excerpt

Binding of the T-cell receptor complex directs the release of effector molecules and focuses them on the target cell