Ch 8Immunology — Class 12 Zoology, concept-first.

Immunology is the branch of biology devoted to understanding the immune system — the network of cells, tissues, organs and molecules that shields an organism from disease-causing agents in its environ…

Innate immunity — also called non-specific or natural immunity — is the resistance to infection that an individual is born with, rather than resistance built up through prior exposure to a particular…

Unlike innate immunity, acquired immunity develops after birth and is targeted at a specific pathogen the body has encountered.

When a pathogen meets the immune system for the very first time, the resulting primary immune response is comparatively slow: the system must first learn to recognise the antigen, then mount antibody…

A lymphoid organ is any organ or tissue involved in the origin, maturation and proliferation of lymphocytes — the immune system's principal specialist cells.

The thymus is a flat, bilobed organ that sits behind the sternum, above the heart. Each lobe is subdivided into many lobules, separated from one another by connective-tissue septa, and each lobule its…

The lymph node is a small, bean-shaped structure and usually the very first site where an antigen entering the tissue spaces is intercepted.

Blood carries a defined mixture of immune cell types. Lymphocytes make up roughly 20–30% of white blood cells and are recognisable by a large nucleus that fills most of the cell, surrounded by only a…

The word antigen (Ag) is used in two related senses: a molecule that generates an immune response, and a molecule that reacts with antibodies once that response exists.

Antibodies are immunoglobulin (Ig) proteins synthesised in response to antigen exposure, and each one binds specifically to the antigen that provoked its production.

The reaction between antigen and antibody is the molecular basis of humoral (antibody-mediated) immunity, and it proceeds in three stages: first, the antigen and antibody physically combine to form an…

A vaccine is a biological preparation that confers active acquired immunity against a specific disease, typically made from weakened (attenuated) or killed forms of the causative microbe, its toxins,…

Vaccination is the process of administering a vaccine into the body — the deliberate act of introducing the preparation to trigger protection against a specific disease.

Allergy is the exaggerated response of the immune system to certain environmental antigens that most people tolerate without incident; the term itself combines 'allo' (altered) and 'erg' (reaction).

Immunodeficiency results from the failure of one or more components of the immune system. Primary immunodeficiencies trace back to genetic developmental defects, while secondary immunodeficiencies ari…

Autoimmunity is an abnormal immune response in which the immune system fails to properly distinguish self from non-self and attacks the body's own tissues.

A tumour (neoplasm) is a mass of cells whose growth has escaped normal control. When such a tumour keeps growing and invades surrounding healthy tissue, it is called cancer; cancer cells that spread f…

The chapter's Evaluation section contains thirty questions in two parts. Questions 1–14 are multiple-choice items covering terminology and mechanisms from across the whole chapter — colostrum and pass…

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