Introduction to the Immune System - Slide Deck

Immuno Exam 1 - Basic Science Core

What Comprises the Immune System? (3 Groups)

• 1) Cells

• 2) Protein/Chemicals

• 3) Organs and Tissues

Basic Functions of the Immune System (3)

1) Identifies and eliminates pathogens

2) Promotes healing and tissue repair

3) Develops long-term immunity

Blood Composition (2)

1) Plasma

2) Formed Elements

How is blood seperated

• With a Centrifuge

• A Centrifuge spins blood to separate it

What are the Formed Elements

1) RBCs (erythrocytes)

2) WBCs (leukocytes),

3)) platelets (thrombocytes)

The plasma contains: (3)

1) H2O

2) Solutes

3) Plasma proteins

Serum

• is plasma minus its clotting factors.

Plasma Proteins (3)

• 1) Albumins

• 2) Fibrinogens

• 3) Globulins

Where is Red Bone Marrow Found? (3)

1) Flat bones

• (sternum, ribs & cranial bones)

2) Irregular Bones

• (coxal bones, vertebrae (singular – vertebra) and scapulae (singular – scapula)

3) The epiphyses (singular – epiphysis) of long bones such as the femur and humerus

Gross Anatomy of Long Bones

Where is Yellow Marrow found?

• Medullary cavity

In cases of severe blood loss, the body can convert yellow marrow back to red marrow to increase blood cell production.

Lifespan of WBCs (5 Types)

• Neutrophils: 1-3 days

• Monocytes: 1-3 days

• Eosinophils: 4-8 days

• T & B Cells: Years

• Basophils: Hours

Process of making White Blood Cells

Multipotent Hematopoietic Cells → Myeloid → Speciallized WBC (Except T & B Cells)

Process of making T, B & Killer Cells

Multipotent Hematopoietic Cells → Lymphoid→ T, B & Killer Cells

Neutrophils (3)

• Nucleus typically divided into 3-5 lobes which are connected by thin strands of chromatin

• Most Common white blood Cell (~60-70%)

• Function is primary defense against bacteria and fungi

• Large numbers of neutrophils will invade tissues where an infection has occurred

Neutrophils Phagocytosis (5 Steps)

• A neutrophil uses its membrane to make a pseudopod to ingest pathogens.

• A lysosome creates particles to destroy the pathogen.

• After it is destroyed, the debris is called the residual body, which is then dumped before another cell is eaten.

Eosinophils

• Nucleus typically divided into 2 lobes

• Almost all of the cytoplasm appears filled with granules

• Granules are not neutral but stain red or pink

• Main function → defense against parasitic infections

Basophils

• Nucleus usually has 2-3 lobes

  • The lobes are typically not as well defined (May be “S” Shaped)

• The granules of basophils are usually stained deeply bluish or reddish-violet

• Less Granules

• Stores lots of Histamines

HISTAMINE

• causes some of the symptoms of an allergic reaction

• Found in Basophils

Monocytes

• C Shaped (Kidney Bean Shape)

• Few to no granules

• become MACROPHAGES when they migrate to tissue

• Monocytes can also become DENTRITIC CELLS

Macrophages

• They are formed by Monocytes when they migrate to tissues

• Macrophages kill intracellular microorganisms (certain bacteria, fungi) similar to neutrophils (i.e., phagocytosis)

• Macrophages also promote inflammation and participate in wound healing and tissue repair

Dendritic Cells

• Specialized antigen-presenting cells crucial for activating the adaptive immune response (more on this in a future lecture)

• Also formed by monocytes

Lymphocytes

• Lymphocytes are generally the smallest of all the WBCs → usually a tad larger than RBCs

• Round nucleus & very little cytoplasm

• Few to no granules

• Two main types → B and T lymphocytes (indistinguishable microscopically)

• Third Type is Killer T Cells

• The function of T cells and B cells is to identify “non-self” antigens, particularly on viruses

B lymphocytes (2)

• Acts as antigen-presenting cells

• When a B lymphocyte encounters a specific antigen, it can become activated and either differentiate into a PLASMA CELL or MEMORY B CELL.

Plasma cells

• Plasma cells produce large quantities of ANTIBODIES which then attack bacteria and viruses.

• Type of B lymphocyte

T Lymphocytes

• HELPER T CELLS or CD4 + CELLS (Which disease is characterized by low counts of these cells?), produce chemicals that direct the immune response.

• While other T cells, called CYTOTOXIC T CELLS or CD8 + CELLS, produce enzymes which induce the death of pathogen infected cells.

Memory B Cells

Following activation, B and T lymphocytes can “remember” the antigens

they have encountered. Throughout the lifetime of an individual, they will

recall each specific pathogen encountered, and are able to mount a strong

and rapid response if the pathogen is ever detected again

Natural killer cells

• a type of lymphocyte that play a major role in the rejection of tumors and cells infected by viruses.

• They kill cells by releasing small cytoplasmic granules of proteins called perforin and granzyme that cause the target cell to die.

Complete Blood Count (CBC)

• used as a broad screening test to check for such disorders as anemia, infection, and many other diseases.

• It is actually a panel of tests that examines different parts of the blood

Tests We need to know about CBC (2)

• White Blood Cell Count

• WBC Differential Count

White Blood Cell Count

• Count of the actual number of white blood cells per volume of blood

• May be increased (LEUKOCYTOSIS) with infections, inflammation,

  cancer, leukemia

• May be decreased (LEUKOPENIA) with some medications, bone

  marrow failure, chemotherapy, and congenital marrow aplasia

  (marrow doesn't develop normally)

• Normal is (3.4 to 10.5)

LEUKOCYTOSIS vs LEUKOPENIA

• LEUKOCYTOSIS (too much WBC)

• LEUKOPENIA (too little WBC)

WBC Differential Count

• Counts the percentage of white blood cells in blood, 5 types tested

• Try to narrow down why specifically the total white blood cells is high

• Include band Neutrophils (Immature Neutrophils)

Lymph

• Lymph is a fluid that is:

  • created in the interstitial spaces of tissues (found in spaces between cells)

  • carried away by lymphatic vessels

  • put back into the circulation through the blood

  • Mixes with the blood

Fluid Exchange Between Compartments (Lymph)

• Lymph is leftover liquid and nutrients dropped by the blood, which is eventually brought back to the blood

Edema (2 Types)

• Definition: palpable swelling due to expansion of extracellular fluid

• Two Types:

  • Pitted

  • Non Pitted

Pitted Edema

• A finger pressed into the skin over an accumulation of fluid resulting in a temporary depression in the skin

• Normal skin and subcutaneous tissues quickly rebound when the pressure is released.

Non-pitted Edema

• Excess fluid in the interstitium becomes infiltrated with protein or other material so that it cannot move freely within the tissue spaces.

Lymphatic Vessels

Lymphatic Capillaries → Lymphatic Venules & Veins → Lymphatic Ducts (Right Lymphatic Duct & Thoracic Duct)

Lymph Nodes

• Lymph nodes are “beads” or “swellings” along certain lymphatic vessels.

• They are FILTERS!

• Most extensive in the breast, neck, axilla, abdomen, thorax, pelvis & groin

• Found in the Lymphatic Venules & Veins

How many lymphatic ducts are there?

• 2 (the right and left)

• Both drain into the subclavian veins (right and left)

Thymus Gland

• Located in the upper chest in front of the ascending aorta and behind the sternum

• Active during childhood and adolescence; gradually shrinks in adults

• T lymphocytes “mature” in the thymus after produced in the bone marrow

  • The thymus “teaches” the T cells how to recognize self vs. non-self antigens

Tonsils

Tonsils are essentially clusters of WBCs hanging out in the pharynx.

• There are 3 types:

  • Pharyngeal (adenoids)

  • Palatine

  • Lingual

Spleen

• Located in LUQ

• Removes dead/deteriorating RBCs, WBCs, and platelets from the circulation

• Can store or “pool” blood, which can be released into the circulation when needed (e.g., hemorrhage) Particularly pools lymphocytes, where they can be presented with antigens and produce antibodies Often injured in abdominal trauma

Splenectomy = removal of spleen

Splenectomy

Removal of spleen

Mucosa associated lymphoid tissue (MALT) (GI Tract)

• Small concentrations of lymphoid tissue the walls of tissue throughout the body.

• MALT is populated by T lymphocytes, B lymphocytes and macrophages, each of which are well situated to encounter pathogens trying to enter the body.