The Immune Response

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THE ANTIGEN ON THE SURFACE OF A PATHOGEN IS IDENTIFIED AS FOREIGN, TRIGGERING AN IMMUNE RESPONSE

1. PHAGOCYTOSIS

Phagocytes engulf pathogens

contained in phagocytic vesicle

joins with lysomsome: pathogen broken down by enzymes and expelled using exocytosis

Phagocyte displays foreign antigens on its surface to trigger immune response

2. PHAGOCYTES ACTIVATE T-CELLS

a) T-Killer Cells destroy infected cells by secreting toxins - reduces the spread of the pathogen. They also secrete enzymes to digest this

b) T-Helper Cells release cytokines, which stimulate B-Cells to divide and produce more antigens, and phagocytes to digest more

3. T-CELLS ACTIVATE B-CELLS

T-Helper Cells stimulate B-Cells to divide more

B-Cell with antibody that is complementary to foreign antigen divides by mitosis to produce memory cells and plasma cells

Memory cells are stored, along with their useful antibodies

4. PLASMA CELLS SECRETE ANTIBODIES

Stimulate antibodies specific to the detected foreign antigen.

These:

Coat pathogen, making it easier for phagocytes to engulf

Bind to and neutralise the toxins produced by the pathogen

Immune response