4.1.1 (12.6) Specific immune system (OCR A-Level Biology)

ANTIBODIES:

  • Y-shaped glycoprotiens called immunoglobulins

  • Two chains held together by disulfide bridge (heavy + light)

  • Bind with Antigen on pathogen to form antigen-antibody complex

  • HOW ANTIBODIES DEFEND

    1. Acts as Opsonin signaling for phagocytosis

    2. Pathogens can no longer effectively invade in this form

    3. Act as Agglutinins casuing pathogens to clump together

    4. Act as Anti-toxin by binding to toxins and making them harmless

Matured in:

Function

T-Helper cells

Thymus gland

Receptors which bind to surface antigens

Produces interleukins (cytokine-cell signalling molecule)

Interleukins stimulate:

  • B-cell activity

  • Antibody production increased

  • Attracts + stimulated macrophages for phagocytosis

T-Killer cells

Thymus gland

Destroy pathogen due to chemical they produce called perforin (makes holes in pathogens cell membrane)

T-Memory cells

Thymus gland

Immunological memory

Live for a long time

If they meet antigen for a second time, divides rapidly to form large amount of clones for T-Killer cells

T-Regulator cells

Thymus gland

Supresses immune response after Pathogen is dealt with

Prevents auto-immune dsease

Plasma cells

Bone Marrow

Produces antibodies to particular antigen and have them put into circulation

Only active for a couple days but makes thousands of antibodies

B-Effector cells

Bone Marrow

Divides to form plasma cell clones

B-Memory cells

Bone Marrow

Immunological memory

Live for a very long time

Programmed to remember a speicifc antigen and can provide a very rapid response if encountered again

DIFFERENCES BETWEEN T AND B LYMPHOCYTES:

  1. B-cells in Bone Marrow, T-cells matured in the B-cellsThymus

  2. B-cells produce antibodies, T-cells do not

  3. B-cells become part of the adaptive immune system, T-cells have a faster + more potent response

CELL-MEDIATED IMMUNITY: T-Cells respond to cells in organism that have experienced some kind of change (Eg: viral infection)

  1. Macrophages engulf + digest pathogens (phagocytosis) and then present the antigens on the pathogens’ surface to make it an antigen-presenting cell (APC)

  2. T-helper cells become activated + produce interleukins stimulating T-cells to divide rapidly

  3. T-Cells then develop into:

    1. T-Memory

    2. Interleukins to stimulate phagocytosis/B-Cell division

    3. Stimulate T-Killer cell clone development to kill infected cells

HUMORAL IMMUNITY