Innate and Active Immune Responses

Immune Response:

• Non Specific (Innate)

Compliment

Vocab:

• Innate

  • Born with it, dont have to develop it

• Pathogen

  • Causative agent; anything causing disease

• Leukocytes

  • White blood Cells (WBC)

  • Macrophages - big eaters

  • Neutrophils - foot soldiers

• Phagocytosis

  • Engulfing and digesting something

• Cytokines

  • Chemicals released by WBC

  • Chemokines 

    • A type of cytokine that attracts other WBC to the area

First Line of Defense: Skin and Mucous Membranes

Secretions:

• Entrance:

  • Surface of Skin

  • Nasal Passages

  • Respiratory

  • Tear ducts

  • Digestive tract

  • All over you

  • Inside digestive tract

• Defense!

  • Sebum, sweat

  • Mucus

  • Tears (antibacterial and antimicrobial properties)

  • Stomach acid (defense against lipid layerd bacteria)

  • Bile

  • Normal microbiota or microbiome

• Past these defenses:

  • Phagocytic cells (macrophages and then neutrophils

  • Inflammation

  • Fever

  • Complement system

Macrophages are SO important

• They perform phagocytosis

• They release chemokines to alert more phagocytic cells (Neutrophils)

• They release pyrogens to influence hypothalamus to create a fever

  • Fevers raise body temperature and constrict blood vessels

• They interact with specific immune cells

Neutrophils

• Neutrophils are in greater number in the body (50-70% in WBC)

• Neutrophils also do phagocytosis

• Neutrophils are the foot soldiers

Some WBC can release histamines that make inflammation happen:

• Inflammation is increased blood flow to the area amd makes capillaries leak fluid into the area (increasing WBC in area)

• Signs include: redness, heat, swelling, and pain

• Examples include: Bug bites

Complement System:

• ~30 proteins circulate in the blood and can be activated by:

  • Classical pathway - activated by the specific immune defense

  • Alternative pathway - C3 protein binding directly to pathogen

• Effects:

  • Activates inflammatory response

  • Acts as opsonin to increase phagocytosis (Opsonization)

  • Activates cascade to trigger MACs (Membrane attack complexes)

    • Large holes in membranes of gram negative bacteria & enveloped viruses.

    • A “tube” or “ring” of proteins inserted into the membrane

Immune Response:

• Specific (Adaptive)

Humoral

Vocab:

• Adaptive - Develops after you are born

• Antigen- Foreign substance that generates an immune response (part of the bad guys)

• APC- Antigen Presenting Cells - WBCs that present antigen to other immune cells, alerting them to something in the body

  • Macrophages

• Lymphocyte - type of WBC that are specific to a pathogen

  • Helper T cells - alert the other lymphocytes

  • Cytotoxic T (Killer T) Cells - Kill infected body cells

  • B Cells - antibody factories!

• Effector = fancy way of saying activated

• Antibody - Y-Shaped protein, produced by B cells (part of the good guys)

  • MAIN DEFENSE!

How does the specific Immune response get triggered?

• Macrophages are the key!!!

• They present antigen to the Helper T Cells and activate the entire chain of events*.

  • *Start both the pathways - cell-mediated and humoral!

Cell Mediated Pathway:

What cells are involved?

• Macrophages (APCs)

• Helper T Cells

• Cytotoxic T Cells – only attack your own body cells that are infected

1. APCs present antigen to Helper T cells and Helper T Cells are activated

2. Helper T cells go into mitotic phase and copy themselves – most are Effector Helper T Cells but some are Memory T cells (distribute throughout body and remain in tissue)

3. Effector Helper T Cells secrete Interleukins (stimulate Cytotoxic T cells and B cells)

4. Effector Cytotoxic T cells recognize infected body cells, release perforans and destroy cell.

Humoral Pathway:

What cells/substances are involved?

• B Cells – activated by interleukins released by Helper T Cells

• Plasma Cells – antibody-secreting cells

• Memory B cells – dormant cell

• Antibodies

1. Interleukins released by Effector Helper T Cells activate B Cells.

2. APC (or sometimes just antigen itself) binds to B Cell receptors.

3. B Cell proliferates and differentiates into Plasma Cells and Memory B Cells.

4. Plasma Cells secrete antibodies which bind to antigens

5. Memory B Cells can respond rapidly to a second infection from same pathogen

Antibodies are AWESOME! Why?

• Highly specific - only bind to one antigen.

  • Only one strain of the cold or the flu for example….

• What can they do?

  • Initiate the complement system

  • Viral inhibition

  • Neutralizing toxins

  • Increase phagocytosis

  • Clump up the pathogens

Types of Antibodies:
Immunoglobulin – another name for antibody

•  *IgG in plasma and tissue – effective against bacteria, viruses, and toxins and activates complement.  ~80% of antibody content

  •  *most abundant

  •   Involved in secondary antibody response

  •   Maternal antibody – lasts  ~6 months

•  IgA in breast milk, tears, nasal fluid, bile, urine

•  IgM develops in plasma and activates complement

  • Involved in primary antibody
    Response

  • “Ig Massive”

  • Involved in the first time you meet a specific pathogen

•  IgD on surfaces of B cells

•  IgE associated with allergic reactions
  
  

Memory Cells = Immunity

• Both B cells and T cells create Memory Cells!

• Memory Cells react to the antigen without having to be activated by any other immune cells.

  • Memory T Cells can kill infected body cells without being activated by Helper T cells.

  • Memory B cells make antibodies without being activated by Helper T Cells.

• This is what gives you immunity!

Secondary Antibody Response:

 Memory B cells remain in lymphoid tissues

 If come into contact with antigen (and pathogen) again

• Divide and mature into plasma cells

• Produce antibodies

• Neutralization of pathogen (usually without symptoms)