Microbiology Chapter 15: Host Defenses I

Flashcards covering the first, second, and third lines of host defense, blood components, types of leukocytes, and mechanisms of the innate immune response.

First-line defenses

Barriers that block invasion at the portal of entry, such as skin, mucous, hair, and stomach acid.

Second-line defenses

Internalized system of protective cells and fluids, including phagocytes, fever, inflammation, and antimicrobial proteins.

Third line defenses

Adaptive immunity involving B cells and T cells.

Innate skin barriers

Factors that make skin a good barrier against microbes, including pH, electrolytes, and keratin.

Lysozyme

An enzyme found in tears, saliva, semen, and breast milk that hydrolyzes peptidoglycan in bacterial cell walls.

Microbial antagonism

The process where established cultures of microorganisms prevent the intrusion of foreign strains of microbes.

Nonspecific chemical defenses

Substances like sebaceous secretions, lysozyme, lactic acid, electrolytes, oils, and waxes.

Cilia

Hair-like structures responsible for the movement of mucus.

Microvilli

Cellular extensions that function to increase the surface area.

Immune system responsibilities

The three main duties of a healthy immune system: Surveillance, recognition, and destruction.

Markers

Molecules on cell surfaces composed of proteins and/or sugars that are evaluated by the immune system for pathogen recognition.

Body compartments of the immune system

The four participating compartments: mononuclear phagocyte system, extracellular fluid ($ECF$), bloodstream, and lymphatic system.

Mononuclear phagocyte system ($MPS$)

A support network of connective tissue fibers and reticular system originating in the basal lamina that interconnects tissues and organs.

GALT

Gut Associated Lymphoid Tissue.

MALT

Mucus Associated Lymphoid Tissue.

SALT

Skin Associated Lymphoid Tissue.

BALT

Bronchial Associated Lymphoid Tissue.

Lymphatic fluid

A plasma-like liquid made of water, dissolved salts, and $2$ to $5\%$ protein that transports white blood cells, fats, and infectious agents.

Thymus

A triangular organ in the pharyngeal region specializing in T cell maturation that decreases in size with age.

Spleen (Primary function)

The removal of worn-out red blood cells from circulation.

Spleen (Immunologic function)

Filtering pathogens from the blood for phagocytosis by macrophages.

Lymph node

Small, encapsulated, bean-shaped organs stationed in clusters along lymphatic channels, with major aggregations in the armpit, groin, and neck.

Serum

The liquid portion of blood without clotting factors, used in immune therapy.

Plasma

The liquid portion of blood containing clotting factors.

Buffy coat

The layer in un-clotted blood where white blood cells ($WBCs$) are found.

Fibrinogen

A protein involved in blood coagulation.

Hematopoiesis

The production of blood cells, which in adulthood occurs in the red bone marrow.

Stem cells

Immature or unspecialized cells that can develop into specialized mature cells.

Erythrocyte

Red blood cells.

Leukocyte

White blood cells.

Thrombocyte

Platelets.

Megakaryocyte

The cell type responsible for making platelets.

Granulocytes

Leukocytes with a lobed nucleus and cytoplasmic granules that stain with eosin or methylene blue.

Agranulocytes

Leukocytes with an unlobed, rounded nucleus and no granules.

Neutrophils

The most abundant circulating leukocytes ($55\%$ to $90\%$) which act as first responders and perform phagocytosis.

Eosinophils

Granulocytes containing peroxidase and lysozyme that attack and destroy large eukaryotic pathogens.

Basophils

Granulocytes making up less than $0.5\%$ of circulating $WBCs$ that share functional characteristics with mast cells.

Mast cells

Cells that trigger local inflammatory reactions and are responsible for many allergic reactions.

Monocytes

Agranulocytes that differentiate into macrophages and dendritic cells.

Humoral immunity

The branch of the immune system for which B cells are responsible.

Cell-mediated immunity

The branch of the immune system for which T cells are responsible.

Phagocytosis

The process of discovering microbes, recognizing antigens, and then ingesting and eliminating foreign or dead material.

Phagosome

A vacuole created from ingested extracellular material.

Phagolysosome

The structure formed by the fusion of lysosomes and a phagosome, leading to bacterial death within $30$ minutes.

Reactive oxygen products

Oxygen-dependent killing systems including the hypochlorite ion ($OCl^-$), superoxide anion, singlet oxygen, and hydroxyl free radicals.

PAMPs

Pathogen-associated molecular patterns such as Peptidoglycan, Lipopolysaccharide, and double-stranded RNA.

Five signs of inflammation

Rubor, Tumor, Dolor, Calor, and loss of function.

Cytokine

Cell signaling molecules.

Chemokine

Chemotactic factors.

Exogenous pyrogens

Fever-inducing substances originating outside the body, such as endotoxins, vaccines, or infectious products.

Endogenous pyrogens

Fever-inducing signals originating inside the body, specifically Interleukin-1 ($IL-1$) and tumor necrosis factor ($TNF$).

Interferon

A cytokine that inhibits virus replication and can be used to treat viral infections.

Complement pathways

The three pathways of the complement system: Classical, Lectin, and Alternative.

Membrane Attack Complex ($MAC$)

The end result of all three complement pathways.