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Adaptive Immunity: B and T Cells, Antibodies, and Immune Memory

← Builds on Innate Immunity: Barriers, Cells, and Mechanisms

Terms you will need

  • b cellsB cells are a type of white blood cell that helps fight infections by making antibodies, which are proteins that help the body recognize and attack harmful substances.
  • t cellsT cells are a type of white blood cell that helps the immune system by directly attacking infected cells or by helping other immune cells respond to infections.
  • antibodiesAntibodies are proteins made by B cells that help the body recognize and neutralize harmful substances like bacteria and viruses.
  • immunoglobulinImmunoglobulin is another name for antibodies, which are proteins that help the immune system fight infections by recognizing and neutralizing harmful substances.
  • iggIgG is a type of antibody that helps the immune system fight infections by recognizing and neutralizing harmful substances like bacteria and viruses.
  • igmIgM is a type of antibody that is one of the first to respond to an infection, helping the immune system recognize and neutralize harmful substances.

How this topic runs

  1. 1Start here
  2. 2How it works
  3. 3At competition depth

The adaptive immune system is a specialized part of the immune system that protects the body from pathogens by creating highly specific responses. Unlike the innate immune system, which responds to general threats, the adaptive immune system targets specific invaders and remembers them for future encounters. This system is essential for long-term immunity and forms the basis for vaccination. It involves two main types of lymphocytes: B cells and T cells. B cells produce antibodies that neutralize pathogens, while T cells directly attack infected cells or help coordinate the immune response. The adaptive immune system also creates immunological memory, allowing the body to respond more quickly and effectively to pathogens it has encountered before.

Figures (10)

Each antibody binds to a specific antigen in a highly specific interaction analogous to a lock and key.
Schematic structure of an antibody: two heavy chains (blue, yellow) and the two light chains (green, pink). One of the antigen binding sites is circled.
Some antibodies form complexes that bind to multiple antigen molecules.
Antibodies (A) and pathogens (B) free roam in the blood.The antibodies bind to pathogens, and can do so in different formations such as:opsonization,neutralisation, andagglutination.A phagocyte (C) approaches the pathogen, and the Fc region (D) of the antibody binds to one of the Fc receptors (E) of the phagocyte.Phagocytosis occurs as the pathogen is ingested.
Clonal expansion and monoclonal versus polyclonal proliferation
Model of an antibody showing beta strands
Surface model of an antibody at the molecular level
The secreted mammalian IgM has five Ig units. Each Ig unit (labeled 1) has two epitope binding Fab regions, so IgM is capable of binding up to 10 epitopes.
The complementarity determining regions of the heavy chain are shown in red (PDB: 1IGT​)
Simplified overview of V(D)J recombination of immunoglobulin heavy chains

Adaptive immunity is the body's way of fighting infections it has already met. It uses special cells called B cells and T cells. These cells remember past invaders and act faster if they return.

B cells make antibodies. These are proteins that stick to harmful germs and stop them from causing damage. When a germ is tagged by an antibody, other parts of the immune system can destroy it more easily.

T cells do different jobs. Some T cells kill infected cells directly. Others help B cells and other T cells by sending signals.

T cells also remember past infections, so they can react faster next time. These cells stay in the body for years. This is why some diseases, like measles, only happen once in a lifetime.

Key Points

  • B cells are a type of lymphocyte involved in the humoral immune response, producing antibodies to neutralize pathogens.
  • T cells are a type of lymphocyte involved in cell-mediated immunity, playing a role in directly attacking infected cells and regulating immune responses.
  • Antibodies are proteins produced by B cells that bind to specific antigens, neutralizing pathogens and marking them for destruction.
  • Immunoglobulin is a term for antibodies, which are large Y-shaped proteins used by the immune system to identify and neutralize antigens.
  • IgG is a class of immunoglobulin that is the most abundant antibody in human blood and provides long-term immunity.
  • IgM is a class of immunoglobulin that is the first antibody produced in response to an initial infection and is effective at activating the complement system.

Terms

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