Sorting Out Immune System Vocabulary

These notes are based on the book How the Immune System Works by Lauren Sompayrac

Types of Blood Cells

• Stem cell - self-renewing cells located in bone marrow that produce two classes of blood cells.
• Lymphocytes
  • B cell
  • Helper T (Th) Cell
  • Killer T Cell
  • Natural Killer (NK) Cell
• Others
  • Dendritic Cell
  • Macrophage
  • Neutrophil
  • Eosinophil
  • Mast Cell
  • Megakaryocyte
  • Erythrocyte

Erythrocytes are called Red Blood Cells. They carry oxygen, but are not part of the immune system.

All others are leukocytes also called White Blood Cells and are involved in the immune system.

Monocytes are immature macrophages or dendritic cells circulating in the blood prior to emerging for action.

Killer T cells are also called cytotoxic lymphocytes (CTL).

Macrophages are stationed throughout possible entry points and wait for an attacker to eat.

Dendritic Cells carry antigens to lymph nodes and present them to activate helper T cells and killer T cells.

The lymph system is where immune information is shared and B and T cells are activated.

Eosinophil cells and mast cells work with IgE antibodies (see below) to attack parasites.

Mast cells are very long-lived (years), full of granules that can dissolve proteins. They degranulate when triggered by IgE antibodies attached to parasites. They also can opsonize bacteria and give off cytokines that attract neutrophils.

Antigens are the targets of the immune system

Epitopes are the specific parts of antigens that are targeted.

Cytokines are molecules used for communication between body cells. Examples are interleukins (IL-), interferons (IFN-), and tumor necrosis factors (TNF).

Natural killer cells, macrophages, neutrophils, B cells, and T cells all have activated states.

Innate Immune System

Good for bacteria, fungi, viruses that have not entered body cells

Of limited effectiveness once viruses have entered cells

• Macrophage
• Complement proteins
  • B
  • C1 - makes C3 contraverse which fragments C3
  • C3 - most common with fragments C3a and C3b
  • C5, C6, C7, C8, C9, and others
  • D

  C3b proteins are used to identify targets to be killed by macrophages and activated B cells.

  C5-C9 proteins create a membrane attack complex that kills most viruses and bacteria.

• Natural Killer Cells

  Short half-life of about 1 week because they are so destructive.

  Kill cells that have lipopolysaccharide (LPS) on their membranes but do not have Class I MHC molecules showing.

  Kill cells when stimulated by Interferon-Alpha (IFN-Alpha) or Interferon-Beta (IFN-Beta)

  Can make macrophages hyperactive by producing Interferon-Gamma (IFN-Gamma)

  Hyperactive macrophages produce Tumor Necrosis Factor (TNF) and Interlukin-2 (IL-2) which further stimulates production of IFN-Gamma

• Neutrophils

  Become activiated when they are signaled to leave the blood stream by macrophages when help is needed. Once activated, they die within about 5 days because they are so destructive.

  They leave the blood system through endothelial cells of the capillary walls upon detecting suitable via signals as they flow along the capillary.

Macrophages and neutrophils are collectively called professional phagocytes

Adaptive Immune System

Necessary to deal more completely with viruses that have entered body cells

Antibodies are the components of the immune system that attach to antigens

Antibody classes determined by fc region of antibody

Antibodies are made by B Cells and can attach to organic molecules. Only those that do not attach to self molecules are allowed to mature.

• IgM

  Helps complement system identify antigens

• IgA

  Specialized for use near mucosal surfaces

• IgG

  Helps complement system

  Helps NK cells kill

  Boosts macrophage response

• IgE

  Defends agains parasites, involved in allergies. They trigger mast cells to degranulate.

Antigen presentation molecules

Made by activated B Cells, activated dendritic cells, and activated macrophages. These are collectively called antigen presenting cells (APC).

• Class I Major Histocompatibility Complex (MHC) molecules

  Present to Killer T cells pieces of antigens found inside of body cells

• Class II MHC molecules

  Present to helper and killer T cells pieces of antigens found outside of body cells

Components of Adaptive Immune System

• B Cells

  Activated by Helper T cell with CD40-CD40L match

  Mature in Bone marrow

  Target antigens outside of body cells, can hypermutate to improve specificity

  Produce antibodies attached to surface - B Cell Receptors (BCR)

  Spread free antibodies upon activation

• T Cells

  Mature in Thymus

  Target presented protein antigens from within body cells

  Produce antibody-like molecules attached to surface - T Cell Receptors (TCR)

• Helper T cells

  Activated by cell (B Cell, activated macrophage, activated dendritic cell) with B7-CD28 match and protein antigen presented by Class II MHC

  Activates B cells, Killer T cells, and stimulates innate immune system

  Produce cytokines that guide immune system operation

• Killer T cells

  Destroys virus-infected cells, those with presented protein antigens

• Regulating T cells

Both B and T cells activated by helper T cells have memory forms for future protection

Lymph System (Under construction)

The spleen is a junction between the lymph and the blood systems where helper T cells can meet pathogens and become activated, proliferates, and is injected into the lymph system.

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Last updated: May 26, 2017