External barriers
This tough, keratinized outer layer of the skin serves as the body’s first physical barrier to infection.
What is the epidermis?
These granulocytes are the most abundant leukocytes and specialize in killing bacteria.
What are neutrophils?
These proteins are secreted by virus‑infected cells to warn neighboring cells and activate NK cells and macrophages.
What are interferons?
These cells promote the action of cytotoxic T cells and assist in both humoral and innate immunity by secreting interleukins.
What are helper T cells?
This immunoglobulin is found in mucosal areas and is also secreted in breast milk.
What is IgA?
This protein found in the epidermis makes the skin tough, water‑resistant, and protective.
What is keratin?
These granulocytes combat parasites and play major roles in allergy and inflammation.
What are eosinophils?
This liver‑produced system of circulating globulins becomes activated in the presence of pathogens.
What is the complement system?
These cells directly attack enemy cells and release interferons, TNF, perforins, and granzymes.
What are cytotoxic T cells?
This immunoglobulin functions as a receptor on B cells and helps activate them.
What is IgD?
This acidic film on the skin—made of lactic and fatty acids plus dermicidin—helps inhibit microbial growth.
What is the acid mantle?
These granulocytes release histamine and heparin to promote inflammation and prevent clotting.
What are basophils?
This complement effect coats microbes with C3b, making them easier for phagocytes to ingest.
What is opsonization?
These cells calm the immune response after an attack and help prevent cytotoxic T cells from harming the body’s own tissues.
What are Regulator T cells?
This immunoglobulin binds to receptors on basophils and mast cells and is involved in allergic reactions.
What is IgE?
These antimicrobial peptides in the skin, enhanced by vitamin D, help destroy bacteria, viruses, and fungi.
These agranulocytes include NK cells, T cells, and B cells.
What are lymphocytes?
This complement mechanism forms a pore in a pathogen’s membrane, causing it to rupture.
What is cytolysis by the membrane attack complex?
These cells are defensive proteins soluble in blood plasma and body secretions, or within/on the membrane of some B cells, mast cells, basophils.
What are immunoglobulins (antibodies)?
This is the most abundant immunoglobulin (about 80%) and is the only one that crosses the placenta.
What is IgG?
This enzyme used by arthropod vectors breaks down hyaluronic acid in tissue gel, allowing pathogens to spread.
What is hyaluronidase?
These cells arise from monocytes and perform phagocytosis and antigen presentation.
What are macrophages?
These innate immune cells patrol the body, bind abnormal cells, release perforins to create holes, and deliver granzymes to trigger apoptosis.
What are natural killer cells?
The part of the antigen that triggers the response; a molecule that is too small to be antigenic in itself, becomes antigenic upon binding to the host, and is a macromolecule.
What is a epitope; hapten?
This immunoglobulin is the most responsive during primary exposure and is responsible for ABO blood group agglutination.
What is IgM?