Immunity, AIDS and Substance Abuse — Part 1: Immunity: visual lesson, ISC Class 12 Biology

Lesson

Immunity

Part 1 — how the body defends itself, from barriers we are born with to the targeted, remembering response we acquire.

In this lesson you will

Describe the physical, physiological, cellular and cytokine barriers of innate immunity
Distinguish active and passive, and humoral and cell-mediated, immunity; name the lymphoid organs
Describe antibody structure and the five classes of antibodies
Explain vaccination, immunisation and autoimmunity

Concept

Innate immunity: four kinds of barrier

Innate immunity is non-specific and present at birth.

Table of the four barriers of innate immunity
Barrier	Examples
Physical	Skin; mucus lining the respiratory, digestive and urogenital tracts traps microbes
Physiological	Acid in the stomach, saliva in the mouth, tears from the eyes
Cellular	Leucocytes: neutrophils (PMNL), monocytes, natural killer cells; macrophages in tissues engulf microbes
Cytokine	Virus-infected cells release interferons that protect nearby cells

Concept

Interferons

Interferons are proteins secreted by virus-infected cells. They act on neighbouring, uninfected cells, making them resistant to further viral infection. They are an example of the cytokine barrier.

Table about interferons
Point	Detail
Made by	Cells infected with a virus
Act on	Nearby healthy cells
Effect	Block viral multiplication, limiting spread
Use in medicine	α-interferon as a biological response modifier, for example in cancer therapy

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