Micro 4110 Quiz 1- Intro to Immune System, Immune Cells, and Immediate Innate Immunity

Times we want the immune system activated:

Infectious agents, tumors, dead/damaged cells

Times we DON’T want the immune system activated:

Harmless/innocuous substances, other body, own body

Definition of Immunity

A state of protection against foreign pathogens or substances

Hallmarks of adaptive immunity

Antigenic specificity, diversity of players, immunologic memory, self/non-self recognition

Clonal Selection

Stem cells in the bone marrow develop into mature B/T cells, then go to the peripheral lymphoid tissue. The B/T cell then recognizes and binds to an antigen, activating the cell

Clonal Expansion

The activated B/T cell proliferates, creating many more copies of itself. Those cells then differentiate into memory cells, plasma cells that create antibodies (from B cells), and helper and sometimes cytotoxic T cells (from T cells).

Antigen

The substance that interacts with an immune response- smallpox after a person has been infected with cowpox

Immunogen

A substance that triggers an immune response AND interacts with the immune response- Cowpox

Humoral Immunity

Adaptive, production of antibodies (B cells), effective against extracellular infections

Cell-mediated Immunity

Adaptive, production of helper T cells and (sometimes) cytotoxic T cells, effective against intracellular infections

Cells involved in Innate Immunity

Granulocytic (neutrophils, basophils, and eosinophils), Mononuclear cells (monocytes and macrophages), Lymphoid cells (Natural killer cells), mast cells, and dendritic cells.

Cells involved in Adaptive Immunity

T and B lymphocytes

Soluble Mediators in Innate Immunity

Complement proteins, and antimicrobial peptides

Soluble mediators in Adaptive Immunity

antibodies

What does innate immunity recognize?

Pathogen broad patterns (PAMPs)

What does adaptive immunity recognize?

Specific epitopes

How are receptor encoded in innate immunity?

Germline (inherited from parents)

How are receptors encoded in adaptive immunity?

Rearranged gene segmentsWh

What does innate immunity do in response to an antigen?

Engulf and destroy, reduce inflammation

What does adaptive immunity do in response to an antigen?

Produce antibodies, kill infected cells

Hematopoiesis

The formation and development of cellular components of blood (RBCs and WBCs).

Hematopoietic Stem Cells

All blood cells differentiate from these, and they can differentiate into more HSCs, Myeloid progenitor cells, or Lymphoid progenitor cells.

Location of hematopoiesis

Depends on the age/state of development of the individual, but is typically in the liver prenatally and in the bone marrow as an adult.

What increases the rate of hematopoiesis

Infections

What decreases the rate of hematopoiesis

antibiotics, steroids, immunosuppressants, and radiationCE

Cells that arise from myeloid progenitors

Neutrophils, basophils, eosinophils, monocytes, macrophages, mast cells and dendritic cells

Cells that arise from lymphoid progenitors

B lymphocytes, helper T cells, cytotoxic T cells and dendritic cells

Granulocytic cells

Neutrophils, basophils, eosinophils (all innate)

Mononuclear cells

Monocytes and macrophages (all innate)

Lymphoid cells

B lymphocytes, T lymphocytes and Natural Killer cells (all adaptive except for NK cells)

Neutrophil

Granulocytic, myeloid, innate, located in blood.

Phagocytic, has a multi-lobed nucleus, first to arrive at inflamed tissue, contains granules filled with degradative enzymes and antimicrobials to ingest and destroy captured cell.

Eosinophil

Granulocytic, myeloid, innate, located in blood.

Defends against helminths and other parasites that are too big for neutrophils to ingest, cytoplasmic granules are released when cells are activated

Basophils

Granulocytic, myeloid, innate, located in blood.

Same response as eosinophils (respond to parasites too big for neutrophils and release cytoplasmic granules upon activation), but also play a role in allergic responses bc histamines are present in they cytoplasmic granules.

Mast Cells

Myeloid, innate, located in skin, connective tissue, and mucosal epithelial tissue.

Differentiates in tissues, and has cytoplasmic granules filled with histamines and proteases. Protects internal surfaces from pathogens (especially parasitic worms), and plays an important role in allergies

Monocytes

Mononuclear, myeloid, innate, located in blood.

Phagocytic to some extent, but not nearly as much as macrophages and neutrophils. Migrates into tissues where they they differentiate into macrophages.

Macrophage

Mononuclear, myeloid, innate, located in almost all tissues

Extremely long lived (as opposed to neutrophils), phagocytic, antigen processing and presentation to T cells (serves as a bridge!). Able to clear dead cells and cell debris, as well as orchestrates immune responses to activate and recruit other immune cells.

Phagocytic Cells

Mostly neutrophils and macrophages, though monocytes too to a small extent.

Differ in location (neutrophils in blood, macrophages in tissues), life span (neutrophils are short-lived while macrophages are long-lived), and extra abilities (macrophages can scavenge dead cells from the body).

Dendritic Cells

Myeloid AND lymphoid, innate (bridge between innate and adaptive), and located under the skin, below mucosa, and in tissues- all areas likely to come in contact with the outside world.

Perform phagocytosis and pinocytosis (drinking lymph around them looking for pathogens), and are the most potent antigen-presenting cells for activating naive T cells.

B lymphocytes (B cells)

lymphoid cell, lymphoid progenitor, adaptive, mature in bone marrow but circulate in blood, lymph ad secondary lymphoid sites.

Have cell surface receptor for antigens, and differentiate into plasma cells (that secrete antibodies), and memory cells.

T lymphocytes

Lymphoid cell, lymphoid progenitor, adaptive, arise in bone marrow, mature in thymus, and circulate in blood, lymph, and secondary lymphoid sites.

Have cell surface receptors, and are divided into helper T cells (that display CD4 protein) and cytotoxic T cells (that display CD8 protein).

Helper T cells

Express CD4 protein on their surface along with their T cell receptors. Secrete cytokines that play roles in activating other immune cells

Cytotoxic T cells

Display CD8 protein on their surface along with their T cell receptors. Can directly lyse the target cell.

Natural killer cells

lymphoid, innate, blood

Nonspecifically cytotoxic against tumor cells and cells infected with viruses, even though they lack an Ag specific receptor. Can directly lyse the target cell just like cytotoxic t cells, only in a much less specific way.

What cells can originate from both myeloid and lymphoid?

Dendritic cells

What cell types play as a bridge between innate and adaptive immunity?

Dendritic cells and macrophages- both act as a professional antigen-presenting cell

What cells are not granulocytes but contain granules?

Natural killer cells and mast cells

What cells have antigen-specific receptors?

T lymphocytes and By lymphocytes

Which cells predominantly circulate in blood?

neutrophils (highest percentage), eosinophils, basophils, monocytes, natural killer cells, b and t lymphocytes

What cells are NOT circulated in blood?

mast cells, macrophages (tissues), and dendritic cells (tissues)

Which cells can be found in healthy tissue?

Mast cells, macrophages, and dendritic cells

What cells can be found in infected tissues?

Neutrophils (first responders), basophils, eosinophils, monocytes.

Anatomical Barriers

Skin and mucous membranes

Physiological Barriers

Fatty acids in sebum, acidic pH in stomach, lysozyme, lactoferrins, surfactant proteins, AMPs (defensins and cathelicidins), S-100 proteins

Skin

Tight epithelial cells, shedding of dead cells, dry salty acidic surface

Mucous membranes

Tight epithelium, sweeping cilia, mucus secretion, natural flushing by tears, urine, peristalsis in GI

Lysozyme

Found in tears, saliva, and mucosal secretions. Degrades peptidoglycan in cell walls without distinguishing between good and bad mcirobes

Lactoferrins

Found in milk, mucosal secretions in intestine, respiratory, and urigenital tract.

Binds to all the free iron in the body, slowing down the growth of the pathogen to let the immune system catch up

S-100 protein

Found in skin, and mucosal/glandular secretions.

Disrupts membranes, killing cells

Surfactant proteins

Found in secretions of the respiratory tract.

Coats bacterial cells, promoting recognition and phagocytosis

Defensins (an AMP)

Found in skin and mucosal epithelia.

Disrupts membranes of bacteria, fungi, protozoa, and disables viruses

Cathelicidins (an AMP)

Found in mucosal epithelia.

Disrupts membranes of only bacteria

AMPs and Complement Proteins

Function as booth immediate innate and early induced innate because they can be produced constitutively or in the presence of a pathogen.

Secreted by epithelial cells and stored in neutrophil granules