MICR 270 Module 1: Introduction

MICR 270 Modules 1 Flashcards

Immune system

The organization of cells tissues and organs defending against infection.

Functions of the immune system

Discriminate: Recognize self vs. non-self.

Eliminate: Eliminate infectious agents.

Dysfunctions of the immune system

Hypersensitivity/Autoimmunity

Immunodeficiency

Antigen

A foreign protein that induces an immune response. “Antibody generator”.

Antibody

Produced in response to antigens. They bind antigens to signal their elimination.

Lymphoid Organs

Shared organs of the immune system and the lymphatic system.

Thymus

Spleen

Bone Marrow

Lymph Nodes

MALT

Primary Lymphoid Organs

Thymus and Bone Marrow

Responsible for the development and maturation of T cells and B cells into immunocompetent cells.

Secondary Lymphoid Organs

Spleen, Lymph Nodes, and MALT.

Lymphatic System

Drains lymph (fluid with white blood cells) from the interstitial space, and returns it to the circulatory system. Lymphatic vessels carry lymph to the heart.

Bone Marrow

Is found within the central cavity of bones and is made up of red and yellow marrow.

Red marrow: is the site of hematopoiesis and B cells development.

Yellow marrow: produces fat and cartilage (an some lymphocyte development)

Thymus

Located above the heart. Flat, bilobed, with a cortex and medulla. Filled with thymocytes, epithelial cells, dendritic cells, and macrophages. It is the site of T cell development.

MALT

Mucosal Associated Lymphatic Tissues. Initiates the immune response.

Contains the GALT and BALT. Including the lamina propria of intestinal tissue, Peyer’s patches, tonsils, and appendix. MALT is filled with various immune cells and is found in the mucus membranes lining the digestive, respiratory, and urogenital systems.

Spleen

Located on the left side under the heart. Large ovoid organ with white and red pulp.

White pulp: Has macrophages, lymphocytes, T cells, B cells, and RBCs. Is the site of immune response development.

Red marrow: contains cords of billroth ( connective tissue with fibrils containing macrophages and monocytes). Filters blood.

Lymph Nodes

Small(1-25mm) bean shaped. Around 600 total. Have a cortex, paracortex and medulla. Filled with dendritic cells, lymphocytes and macrophages. Are found along lymphatic vessels and filter lymph.

Major Histocompatibility Complexes (MHC)

Expressed by near every nucleated cell on their cell surface. Is a sample of the proteins found inside the cell. Helps the immune system differentiate self from non-self.

MHC Class I

In near every nucleated cell

MHC Class II

Found on B cells and dendritic cells

Elimination of pathogens pathway (4)

Entry —> Recognition —> Activation (innate/adaptive) —> Elimination

Innate immunity

Consists of physical, cellular, and soluble barriers. Is an immediate response that is non specific and relies on pattern recognition.

Adaptive immunity

Divided between cell mediated (T cells) and Humoral (B cells) immunity. Has a longer response time but is specific to the antigens and results in immunological memory.

The most ancient immune structure.

Amoebocyte. Gave rise to the phagocyte.

Order of evolution of lymphoid tissues.

GALT —> Thymus/Spleen —> Bone marrow —> Lymph nodes

Evolution of innate immunity

Present in vertebrates, invertebrates, and plants. (Well developed in fruit flies!)

Evolution of Adaptive immunity

Only in subphylum vertebrata. Only well developed in more complex vertebrates.

Infectious Agents

Viruses

Bacteria

Fungi

Protozoa

Helminths

Prions

Bacteria

Unicellular, prokaryotic organisms. have circular ds DNA.

Cholera

A diarrheal bacterial infection cause by the bacteria vibrio cholerae in the intestines. Is mostly mild and can be treated through dehydration and antibiotics.

Viruses

Non living, and rely on a host cell for replication. Are surrounded by a protein coat and sometimes a lipid envelope. Have ss or ds DNA/RNA.

Influenza

A viral infection (strains A and B are the seasonal flu). Spreads through droplets and can be treated with rest and antivirals. There is a preventative vaccine.

Fungi

Heterotrophic eukaryotes. Can be unicellular (yeast), or multicellular (mold). Have a chitin or cellulose cell wall. Reproduce through spores and people are prone to infection during periods of weakened immunity.

Vaginal yeast infection

Vulvovaginal candidiasis. treated with antifungal creams, ointments, or suppositories. itchy.

Protozoa

unicellular, heterotrophic eukaryotes. Have no cell walls allowing for rapid and flexible movement.

Malaria

A protozoan parasite found in mosquitos. preventable drugs are available.

Helminths

Parasitic worms. Multicellular, invertebrate infectious parasites. They have differentiated tissues and can be difficult to treat due to similarities to human animal cells.

Schistosomiasis

Caused by helminths. Inflammation and scarring is caused by the eggs. Symptoms include fever, chills, lymphoid organ enlargement, abdominal pain, and diarrhea. Treated by praziquantel.

Prions

Proteins causing degenerative CNS disorders. Only become infectious when misfolded (local energy minimums make the misfolded state thermodynamically more stable).

Bovine Spongiform Encephalopathy (BSE)

“mad cow disease”. Caused by sheep food infected with scabies. Causes nervousness, aggressiveness, coordination difficulty and weight loss, followed by coma and then death in cows. Not common in humans.

Creutzfeldt Jakob Disease (CJD)

Most common prion infection in humans. Caused by exposure to infected brain tissue or spinal fluid. Can also be inherited. Leads to CNS degradation (dementia, muscle coordination), followed by a coma then death. No available treatment.

Hematopoietic Stem Cell

Divides itself to replace older stem cells. Pluripotent and can divide into many cell types. Once committed it cannot return.

Myeloid Progenitor Cell

Generate the majority of cells involved in innate immunity. Can differentiate into:

Granulocytes

Monocytes

Erythrocytes

Thrombocytes

Lymphoid Progenitor Cell

Differentiate into B, T and NK cells. Generate the adaptive immunity cells.

Erythrocytes

Red blood cells. Generated by hematopoiesis.

Thrombocytes

Platelets. Aid in coagulation, wound healing and fibrinolysis. Have some inflammatory functions.

Monocytes + macrophages

Phagocytes that ingest and destroy foreign particles, bacteria, and cell debris. monocytes reside in the blood but cross vessel walls and become macrophages. macrophages are larger, have increased pseudopodia, phagosomes, lysosomes, and phagocytic ability.

Neutrophils

Most abundant leukocyte. polymorphic nucleus. Has granules containing lytic enzymes (peroxidase, lysozyme). First to arrive to the site of infection but only live a few days.

Dendritic cells

The bridge between innate and adaptive immunity. Arise from myeloid or lymphoid progenitor cells. Engulf antigens and present then to adaptive immunity cells.

Basophils

Non phagocytic granulocytes. Least common granulocytes. Contain heparin and histamine. have a polymorphic nucleus. they are similar to mast cells and are involved in the allergic response. Have the largest granules of the granulocytes.

Eosinophils

Phagocytic granulocytes. Damage parasitic membranes (e.g. helminths) Have a polymorphic nucleus. Have a very minor phagocytic role.

NK (natural killer) cells

Granular lymphocytes. Contain perforin and granzymes to create lesions in target cell membranes and induce apoptosis. Can distinguish abnormal cells despite having no antigen receptors and are involved in innate immunity despite deriving from lymphoid progenitors.

Mast Cells

Granulocytes containing histamine and other substances. play a role in allergy development.

T cells

Cell mediated immunity. Mature in the Thymus. have TCR that are specific to an antigen. Every T cells recognizes a different antigen. (Specificity + Diversity)

Helper T Cells

T_^H or CD4⁺ . Express the CD4 co-stimulatory molecule. Many subsets. Are activated when they recognize MHC Class II.

Effector cells: Activate other immune cells (B cells, CTLs, macrophages)

Memory cells: Generated by Activated T cells and help display a quicker and faster immune response upon reinfection.

Cytotoxic T Cells

CD8⁺ or T_c. Display CD8 co-stimulatory molecule.

Effector cells: Eliminate cells displaying foreign antigen complexes with MHC Class I. Activated by MHC I recognition.

Memory Cells: Activated T_c cells generate memory cells for a quicker and stronger immune response upon reinfection.

B Cells

Humoral immunity. Mature in the bone marrow. Have specific + differentiated BCR.

Plasmacytes

The effector form of activated naive B cells. Create and secrete antibodies that bind free pathogens/foreign molecules.

Memory B Cells

Generated by activated B cells that have membrane bound antibodies. Display a quicker and stronger immune response upon reinfection.