The Immune System

The Immune System can be divided into ___ and ___.

• acquired immunity

• innate immunity

Acquired Immunity

• The immunity developed after exposure to pathogens or through vaccination

• includes T-cell and B-cell immunity

T-cell immunity

• aka cell-mediated immunity

• a form of acquired immunity, where T-cells fight infections by directly killing infected cells

B-cell immunity

• aka humoral (blood composition) immunity

• a form of acquired immunity, where B-cells produce antibodies and memory cells that fight infection

Innate Immunity

• the immunity that we are born with

• includes bloodbourne barriers (phagocytes, neutrophils, macrophages, basophils, etc)

• and physical barriers (skin, mucus membranes, saliva, stomach acid)

Basophils, neutrophils, eosinophils, monocytes, macrophages, and dendritic cells all develop from ___ ___ .

hematopoietic stem cells —> common myeloid preogenitor —> granulocyte monocyte progenitor

T-cells, B-cells, and IL-C all develop from ___ ___.

hematopoietic stem cells —> common lymphoid progenitor

Adaptive Immunity consists of ___ and ___, while innate immunity consists of ___.

• Adaptive Immunity: T-cells and B-cells

• Innate immunity: everything else

What are the three primary leukocytes (WBC)?

• lymphocytes

• monocytes

• granulocytes

Types of granulocytes:

• neutrophils

• eosinophils

• basophils

Neutrophils

• the most common WBC

• are the first response to a pathogen

• functions: phagocytosis and release of antimicrobial compounds (granules)

Phagocytosis

occurs when a cell engulfs a pathogen

What are the two ways a neutrophil may phagocytize a pathogen?

1. they engulf it and then release enzymes to degrade it when it is inside a cell

2. they engulf it partially and release enzymes to degrade it outside the cell (causes DOMS)

Basophils

• the least common WBC

• contains histamine, heparin, and peroxidase within its granules

• function: releases histamine when activated, which increases permeability and size of capillaries —> causing inflammation due to increased blood flow

• plays a major role in allergic response

Antihistamines hinder recovery after exercise. Why?

they block histamine, which causes inflammation and increased blood flow —> as a result, muscles recover slower

Eosinophils

protects the body against parasites and help with the recruitment of basophils during allergic rxns

Monocyte types

• classical

• intermediate

• non-classical

Classical monotypes

• make up the largest portion of monocytes

• are phagocytic cells

Intermediate Monocytes

• develop from classical monocytes

• are involved in antigen presentation and inflammation

Antigen presentation

allows T-cells to recognize a specific antigen and respond to a pathogen

Non-classical Monocytes

are involved in patrolling and T-cell proliferation (pro life = production)

Classical monocytes may transition to ___ ___.

M1 macrophages

M1 Macrophages

• participate in phagocytosis

• produce secondary damage

• supports MPC proliferation (production)

• secretes IGF-1

M2 Macrophages

• secrete IGF-1s

• supports MPC differentiation

M1 and M2 macrophages are needed for…

a full recovery

Natural Killer cells

• are apart of the innate immunity

• recognize and kill infected / tumor cells

• NK cells bind to antibody-coated targets

• recognize the lack of MHC class I molecules

MHC class I molecules

each cell in your body has a protein / something identifying it as you. If a cell doesn’t have it, NK cells start attacking it

T-cells recognize…

fragments of antigen bound to MHC molecules

Types of T-cells

• T-helper

• T-cytotoxic

T-cytotoxic cells

kill cells that have a virus and MHC class 1 antigens

T-helper cells

helps with the immune response by stimulating various cells (B-cells, T-cells, macrophages)

Cytokines

• soluble proteins that allow for communication between cells

• there are various types, all with varying functions

What produces cytokines (4)?

• all WBCs

• skeletal muscle

• adipose tissue

• endothelial cells

Antibodies

proteins that identify, bind to, and fight harmful invaders (such as bacteria and viruses)

Types of Antibodies

• IgA

• IgE

• IgD

• IgG

• IgM

IgA

• fights infection in mucosal membranes

• provides passive immunity to infants through breast milk

IgE

• triggers the release of chemical substances in mast cells and basophils

• helps defend the body against parasites

• triggers allergic rxns

IgD

activates B-cells

IgG

can cross the placenta from mother to fetus, providing the fetus with passive immunity before birth

IgM

• typically the first antibody produced when a pathogen is identified

• activates the complement system, which helps destroy pathogens