Ch 12Immune System — Class 12 Zoology, concept-first.

Immunity is the overall ability of the body to resist and defend itself against disease-causing organisms (pathogens) and other foreign substances (antigens).

Non-specific, or innate, immunity is the immune system's general-purpose, always-ready defence. It does not need to recognise a specific pathogen in advance, and it is traditionally described as actin…

B-lymphocytes (B-cells) are the white blood cells responsible for producing antibodies. They originate and develop in the bone marrow (in birds, this maturation happens in a specialised organ called t…

Mononuclear phagocytes are white blood cells with a single, un-lobed nucleus that defend the body by phagocytosis — engulfing and digesting pathogens and cellular debris.

An antibody, or immunoglobulin, is a Y-shaped protein produced by plasma cells to bind and neutralise a specific antigen.

Humoral immunity is the antibody-mediated arm of the specific immune response, most effective against pathogens and toxins that are free in the body's fluids ("humors") — blood, lymph and tissue fluid…

Cell-mediated immunity is the arm of the specific immune response carried out directly by cells rather than by circulating antibodies, and it is the main defence against pathogens hiding inside host c…

Vaccination (immunization) works by deliberately exposing the body to a harmless or weakened form of an antigen — a killed or attenuated pathogen, or one of its components — without causing the actual…

HIV (Human Immunodeficiency Virus) is a retrovirus with a fairly simple but distinctive structure. Its outermost layer is a lipid envelope, borrowed from the membrane of the host cell it last budded f…

Sample papers and previous-year board questions for this subject.