Describe the components of the innate immune system.
Epithelial barriers that block entry of microbes, phagocytic cells (mainly neutrophils and macrophages), dendritic cells, natural killer (NK) cells, and several plasma proteins, including the proteins of the complement system
What are pathogen-associated molecular patterns? What type of immunity is preprogrammed to react to them?
Certain microbial components that are shared among related microbes and are often essential for infectivity; innate immunity
What innate cellular receptors recognize pathogen-associated and damage-associated molecular patterns?
Pattern recognition receptors (of which, Toll-like, C-like leptin, and NOD-like receptors are a type)
What are two modes of innate reactivity?
Inflammation and antiviral defense
What makes up the adaptive immune system?
Lymphocytes and their products
What are the three main types of T lymphocyte and what do they do?
Helper T lymphocytes stimulate B lymphocytes to make antibodies and activate other leukocytes (e.g., phagocytes) to destroy microbes; cytotoxic T lymphocytes (CTLs) kill infected cells; and regulatory T lymphocytes limit immune responses and prevent reactions against self-antigens.
What does the T Cell Receptor (TCR) sense?
Peptide antigens that are presented by major histocompatibility complex (MHC) molecules on the surfaces of antigen-presenting cells
What two components form the TCR complex?
The TCR and CD3
What is the most important antigen-presenting cell for initiating T-cell responses against protein antigens?
What are the generative lymphoid organs?
The thymus and bone marrow
What are the peripheral lymphoid organs? What is their purpose?
Lymph nodes, spleen, and the mucosal and cutaneous lymphoid tissues;
concentrate antigens and immune cells in a way that optimizes interactions among these cells and the development of adaptive immune responses
What is the germinal center of a lymph node?
A central region of some follicles
What are human MHCs called?
Human leukocyte antigens
What is the function of MHC molecules?
To display peptide fragments of protein antigens for recognition by antigen-specific T cells
Are MHC I molecules expressed on platelets?
What do MHC I molecules display?
Peptides that are derived from proteins, such as viral and tumor antigens, that are located in the cytoplasm and usually produced in the cell, and class I–associated peptides are recognized by CD8+ T lymphocytes
Which HLAs code for MHC I molecules?
HLA A, B, and C
Which HLAs code for MHC II molecules?
HLA D (DR, DP, DQ)
Where do MHC II molecules display?
Antigens that are internalized into vesicles, and are typically derived from extracellular microbes and soluble proteins.
How do adjuvants help to increase immune response to vaccines?
They are microbial mimics
What are the components of a type I hypersensitivity reaction?
The injury is caused by TH2 cells, IgE antibodies, and mast cells and other leukocytes. Mast cells release mediators that act on vessels and smooth muscle and proinflammatory cytokines that recruit inflammatory cells.
Describe type II hypersensitivity reactions.
Secreted IgG and IgM antibodies injure cells by promoting their phagocytosis or lysis and injure tissues by inducing inflammation
Describe a type III hypersensitivity reaction.
IgG and IgM antibodies bind antigens usually in the circulation, and the antigen-antibody complexes deposit in tissues and induce inflammation
Describe the components of a type IV hypersensitivity reaction.
Sensitized T lymphocytes (TH1 and TH17 cells and CTLs) are the cause of the tissue injury
What type of hypersensitivity reactions are allergies?
What is the Arthus reaction (local immune complex disease)?
A localized area of tissue necrosis resulting from acute immune complex vasculitis, usually elicited in the skin after injection with an antigen
What is self-tolerance?
A lack of responsiveness to an individual’s own antigens
What is immunologic tolerance?
The phenomenon of unresponsiveness to an antigen induced by exposure of lymphocytes to that antigen
What is central immunologic tolerance?
Self-reactive T and B cells are killed or rendered harmless