Immune System: Part II

Pyrexia

• aka fever

• a controlled rise in body temperature due to a higher hypothalamic set-point

• triggered by pyrogens released during infection or inflammation

Pyrogens

fever causing substances

Pyrogens are released by…

• neutrophils

• macrophages

• B lymphocytes

• epithelial cells

• glial cells

Describe the process of a fever

1. Pyrogens are released

2. Pyrogens reach the hypothalamus

3. they trigger enzymes that liberate arachidonic acid

4. Arachidonic acid is converted to PGE2

5. PGE2 raises the hypothalamus set-point (acts like turning up a thermostat) and inhibits pathogen reproduction

How does the body respond when the hypothalamic set point rises?

• vasoconstriction —> less blood flow to skin —> feels cold

• shivering —> generates heat

• piloerection (goosebumps) —> traps air

• increased metabolism —> produces more internal heat

You feel ___ when the fever is climbing, and ___ once it is reached.

chilly; hot

What are the body’s temperature reducing responses following a fever?

• vasodilation

• sweating

• increased ventilation

What are the two key functions of the innate immune system?

• immune clearance

• complement

What are the key players in immune clearance?

• RBCs

• CR1

• C3b

• antibodies

What is the main function of immune clearance?

to remove pathogens bound to antibodies / complement via RBCs

What is the outcome of immune clearance?

pathogens are carried to the liver or spleen for destruction

Describe the process of natural immune clearance

1. RBCs act as a transport helper

2. pathogens are tagged with antibodies and complement proteins (C3b)

3. RBCs have receptors called CR1 that bind to C3b on the pathogen

4. The RBCs carry the pathogen to the spleen or liver for destruction

Describe the process of HP (heteropolymer) system immune clearance

• shows an engineered version of the natural immune clearance process

• however, instead of C3b, a heteropolymer links antibodies to RBCs to help the immune system remove pathogens more efficiently

What is the main function of the complement system?

to directly kill pathogens by forming pores

Leukocytes (WBCs)

the body’s disease fighting cells

True or False: WBCs spend little time in the blood stream

true; instead they migrate through capillary walls (a process called diapedesis) and move into connective tissue

Leukocytes make up about ___ percent of your blood.

1%

How long do leukocytes live for?

roughly 10 days

Innate cells

• fast, general, short-term defense

• ex: macrophages, neutrophils, eosinophils, natural killer cells

Macrophages

engulf and digest pathogens

Neutrophils

first responders that fight bacteria

Eosinophils

fight parasites and help with allergic rxns

Natural Killer cells

destroy virus-infected or cancerous cells

Adaptive cells

• slower, specific, long-term defense

• ex: T and B cells

B cells

make antibodies that recognize specific invaders

T cells

• include Helper T cells that coordinate immune responses

• include cytotoxic T cells that kill infected cells directly

Neutrophils, eosinophils, and macrophages practice ____.

phagocytosis to engulf pathogens.

Cytotoxic T cells and NK cells are ____.

cytotoxic, meaning they kill infected or cancerous cells

What do plasma cells produce?

antibodies

What is the most extensive division of human lymphoid tissue?

mucosal macrophages

MALT

mucosal macrophages associated with lymphoid tissue

GALT

mucosal macrophages associated with the gut

BALT

mucosal macrophages associated with the bronchial-associated lymphoid tissue

NALT

mucosal macrophages associated with nasal lymphoid tissue

VALT

mucosal macrophages associated with the vaginal lymphoid tissue

What do antigen presenting cells do?

• label our cells as ours

• cradle antigens on the cell surface, specifically the MHC (major histocompatibility complex)

What are the two types of major histocompatibility complexes (MHC)?

• MHC 1: T cytotoxic

• MHC 2: T helper

What are the things that the Major Histocompatibility Complexes (MHCs) may do?

• program a group of B cells to produce antibodies

• Suppress the production of an antibody

• Directly kill the pathogen

What are examples of humoral immunity?

B cells and antibodies

What are examples of cellular immunity?

T cells and assistive immune responses

What are the four classifications of T Lymphocytes?

1. Cytotoxic T-cells

2. Helper T-cells

3. Suppressor T-cells

4. Memory T-cells

Cytotoxic T-Cells

attack infected or cancerous cells via chemotaxis

Helper T-Cells

an intermediary between innate and adaptive immune cells

Suppressor T-Cells

prevents excessive responses by other T-cells by suppressing them

Memory T-Cells

long-lived cells that remember previous antigens and respond quickly upon re-exposure

Where do B lymphocytes mature?

in the bone marrow

What do B lymphocytes do?

• they migrate to lymph tissues and organs, where they differentiate into plasma cells

• these plasma cells then produce and circulate antibodies; and protect immunoglobulins

What do immunoglobulins do?

• they protect the body from antigens by neutralizing them

• they initiate acute inflammatory reactions to control the spread of antigens and destroy them