Immunology: Innate and Adaptive Immunity

A type of antigen that activates B cells without the help of T helper cells. These antigens have repeating units (epitopes) that can cross-link several antigen receptors on the same B cell, stimulating the B cell to produce antibodies without T cell involvement.

The process of generating a diverse repertoire of antibodies by randomly rearranging gene segments that code for antigen receptors, resulting in variations in the amino acid sequence at the antigen-binding site.

The elimination of potentially harmful B cells that generate antibodies against self-tissues, occurring during the early stages of B cell development in the bone marrow.

The strength of the bond between an antibody and its specific antigen. It is influenced by the fit between the antigen-binding site and the epitope, as well as the attractive forces between their amino acids.

The complex formed when an antibody binds to its specific antigen. This interaction plays a crucial role in immune responses.

The portion of an antibody molecule that interacts with complement proteins, initiating the classical complement pathway, which leads to the destruction of pathogens.

Specialized receptors found on the surface of macrophages that bind to antibodies attached to antigens, enhancing phagocytosis.

One of the five major classes of immunoglobulins, each with a distinct structure and function.

A single antibody molecule, as opposed to a dimer or pentamer.

Two antibody molecules linked together, found in the IgA class.

Five antibody molecules linked together, found in the IgM class.

The process by which B cells generate a diverse repertoire of antibodies by recombining variable (V) and constant (C) region gene segments.

The region of an antibody molecule that binds to specific antigens, composed of highly variable amino acid sequences.

The region of an antibody molecule that is constant within a specific class of immunoglobulins, responsible for effector functions.

The immune system's first line of defense; it responds quickly and nonspecifically to any pathogen. It lacks memory, meaning it doesn't remember past encounters with specific pathogens.

The immune system's second line of defense; it responds specifically to pathogens it has encountered before. It has memory, meaning it can recognize and target the same pathogen more effectively in future encounters.

The ability of adaptive immunity to distinguish between the body's own cells and foreign substances. This ability prevents the immune system from attacking its own tissues.

When the immune system mistakenly identifies the body's own cells as foreign and attacks them. This can lead to various autoimmune diseases.

A procedure involving a weakened or inactive version of a pathogen, triggering an adaptive immune response without causing a full-blown infection. This response 'trains' the immune system to recognize and fight the real pathogen later.

The ability of adaptive immunity to remember specific pathogens it has encountered. This allows for a quicker and more effective response to subsequent infections.

Important cells in the adaptive immune system that are responsible for recognizing and destroying specific pathogens.

When antibodies bind to antigens on the surface of cells, causing them to clump together.

A type of antibody that can recognize the same identical antigen on multiple cells.

A specific part of an antigen that is recognized by an antibody.

The main function of IgG antibodies is to neutralize pathogens by destroying them.

IgG antibodies are small enough to cross the placenta and protect the fetus during development.

IgG antibodies can trigger the activation of the complement system, which helps to destroy pathogens.

IgG antibodies can enhance phagocytosis by making it easier for phagocytes to recognize and engulf pathogens.

IgG antibodies are found in the blood, lymph, and tissues, including the intestines.

The dominant antibody found in human blood, accounting for about 80% of serum antibodies.

IgG antibodies are monomeric, meaning they exist as single Y-shaped molecules.

Antigen-presenting cells (APCs) are cells that display antigens on their surface to activate immune responses. B cells can act as APCs, particularly when they internalize and process antigens. They then present these processed antigens on MHC-II molecules to T helper cells.

B cell receptors (BCRs) are surface-bound antibodies on B cells that recognize and bind to specific antigens. These receptors are typically IgM, a type of antibody that exists as a monomer (single unit) on the B cell surface.

When an antigen binds to the B cell's BCR, the B cell internalizes the entire complex (antigen and receptor) and processes it. The antigen is broken down into fragments and displayed on MHC-II molecules on the B cell surface.

MHC-II molecules present processed antigen fragments to T helper cells. These MHC-II molecules are found on the surface of B cells and other antigen-presenting cells (APCs).

T helper cells (TH cells) express T cell receptors (TCRs) that recognize specific antigen fragments presented on MHC-II molecules by APCs, including B cells. This recognition triggers the TH cells to secrete cytokines.

Cytokines are signaling molecules released by T helper cells (TH cells) that activate B cells and drive their proliferation and differentiation into antibody-producing cells (plasma cells).

When a B cell encounters a specific antigen, it undergoes clonal expansion, meaning it proliferates into multiple daughter cells that all have the same specificity for that antigen.

Plasma cells are mature B cells that are dedicated to producing and secreting large amounts of antibodies. This is their primary function in the adaptive immune response.

Antibodies are proteins produced by activated B cells (plasma cells) that specifically bind to antigens. They play a crucial role in neutralizing and eliminating pathogens from the body.

The process of B cell activation involves a series of steps, beginning with antigen binding to B cell receptors (BCRs) and ending with the differentiation of B cells into antibody-producing plasma cells. This intricate process depends on interactions between B cells, T helper cells, and cytokines.