Adaptive Immunity: Antigens, Antibodies & Lymphocytes

• Acquired (adaptive) immunity involves the use of antibodies to fight pathogens.

Antigens

• Surface substances like lipids, carbohydrates, and proteins stimulate a specific immune response.
• Chemical markers signal the body to produce antibodies.
• Foreign antigens originate outside the body, such as on pathogens.
• Autoantigens originate within the body.

Antibodies

• Y-shaped proteins are produced by lymphocytes.
• Each antigen causes the production of a specific antibody that attaches only to that specific antigen.
• Antibodies must have the right shape to match antigens.
• Antibodies attack toxins and prevent them from attaching to cells and interfering with their function.
• The average body contains more than 10 million antibodies.
• A properly functioning immune system can fight off pathogens asymptomatically.

Lymphocytes

• Lymphocytes, a type of white blood cell, are key to the adaptive immune system.
• Lymphocytes help the body destroy pathogens, remember, and recognize previous invaders.
• There are two kinds of lymphocytes involved: B-lymphocytes and T-lymphocytes.

B-lymphocytes (B-cells)

• B-lymphocytes mature in the bone marrow.
• B-lymphocytes are responsible for producing antibodies.

T-lymphocytes (Helper T-cells & Killer T-cells)

• T-lymphocytes mature in the thymus gland.
• Helper T-cells regulate the production of antibodies by B-cells.
• Killer T-cells directly destroy cells.

The Humoral Response

• The humoral response occurs in the body's fluids.

Antigen Presentation

• When a pathogen invades, a dendritic cell engulfs some pathogens and presents the antigens on its surface.
• Other cells, like B-cells and macrophages, may also display antigens.

T-cell activation

• Activates a fraction of the body's helper T-cells with receptors that match the antigen.
• Some activated helper T-cells become -T cells, while others become effector T-cells.

B-cell activation and differentiation

• B-cells are activated by binding to them
• Activated B-cells proliferate and differentiate into plasma cells and memory cells.
• Plasma cells produce and release antibodies at a rate of 2000/s into the bloodstream.
• Pathogens and infected cells are destroyed by binding antibodies to antigens.
• This process makes pathogens and infected cells easier targets for phagocytes.
• Antibody production during the first antigen exposure is known as the primary immune response.
• Memory cells produce antibodies faster if the same pathogen invades again.
• This faster response is known as the secondary immune response.
• Memory B-cells produce antibodies quickly so disease does not have the opportunity to develop.
• The first exposure to a pathogen causes the body to produce antibodies for future attacks by the same pathogen.

Cell-Mediated Immunity

• Some helper T-cells can attack infected antigen-bearing cells directly (killer T-cells) and destroy the pathogens.
• Also known as cytotoxic T-cells.
• Killer T-cells cause pathogens to rupture and die (apoptosis).
• Killer T-cells reject tissue transplants.

Explore adaptive immunity, focusing on how antibodies combat pathogens. Learn about antigens, the markers triggering antibody production, including foreign and autoantigens. Understand the role of Y-shaped antibodies and lymphocytes in destroying pathogens and creating immunological memory.