Chapter 24: The Innate and Adaptive Immune Systems

Pathogens

Organisms that cause infection, such as bacteria, viruses, or fungi.

Restriction factors

Intracellular proteins in bacteria that defend against viruses.

Innate immune response

General defense actions that can involve any cell type in an organism.

Adaptive immune response

Specific immune reactions that are highly tailored to the particular pathogen that induced them.

Lymphocytes

A class of white blood cells involved in the immune response.

B Lymphocytes

Lymphocytes that secrete antibodies that bind specifically to pathogens.

T lymphocytes

Lymphocytes that can directly kill cells infected with pathogens.

Epithelial surfaces

The outermost layers of skin and lining of respiratory, digestive, urinary, and reproductive tracts that provide physical and chemical barriers to pathogen invasion.

Pattern Recognition Receptors (PRRs)

Receptor proteins that recognize specific repeating patterns called pathogen-associated molecular patterns (PAMPs) on pathogens.

Inflammatory response

A response triggered by the activation of PRRs, resulting in the production of extracellular signal molecules that mediate inflammation.

Phagocytic cells

Cells that engulf and destroy pathogens, such as macrophages and neutrophils.

Complement activation

Activation of a system of proteins that target pathogens for phagocytosis or lysis.

B cells

Lymphocytes responsible for producing antibodies that can bind to specific antigens.

Immunoglobulins

Y-shaped proteins produced by B cells and plasma cells that can bind to specific antigens.

T cells

Lymphocytes involved in recognizing specific antigens and coordinating immune responses.

MHC proteins

Cell surface molecules that present antigens to T cells for recognition.

IgM

It is the first antibody produced during an immune response and is particularly effective at activating the complement system.

IgG

It is the most abundant class of antibodies in the bloodstream and is involved in long-term immunity.

IgA

It is primarily found in secretions such as saliva, tears, and breast milk, providing localized protection on mucosal surfaces.

IgE

It is involved in allergic reactions and defense against parasitic infections.

IgD

It is primarily found on the surface of naive B cells, serving as a BCR.

Cytokines

Helper T cells release chemical messengers called cytokines.

Perforin and Granzymes

Cytotoxic substances released by cytotoxic cells.

MHC proteins

It also known as human leukocyte antigens (HLAs) in humans, are cell surface molecules that present antigens to T cells.