3B Microbio

First line of defense

innate (not acquired); nonspecific; does NOT involve development of immunologic memory

Physical or anatomical barriers

skin (unbroken skin is difficult to penetrate); sweat glands (flush microbes away); mucous membranes and mucous coat (barrier protection); respiratory tract (nasal hairs, ciliated cells)

Nonspecific chemical defenses

lysozyme (enzyme in tears that hydrolyzes peptidoglycan); defensins (peptides that damage membranes and lyse bacteria and fungi)

Genetic barrier example

pathogens have host specificity; some only affect certain species; example: sickle cell anemia provides malaria resistance

Functions of a healthy immune system

surveillance of tissues and organs; recognition of self vs nonself; attack and destruction of foreign invaders

Pattern recognition receptors (PRRs)

molecules on white blood cells that act as “feelers” to detect pathogens (example: Toll-like receptors)

Pathogen-associated molecular patterns (PAMPs)

molecules on pathogens that act as “red flags” for immune detection (example: peptidoglycan)

Reticuloendothelial system

network of connective tissue fibers; provides passageway within and between tissues and organs; contains WBCs of mononuclear phagocyte system; carries extracellular fluid throughout network

Whole blood composition

formed elements (WBCs, RBCs, platelets) plus plasma (liquid portion)

Plasma

contains chemicals, proteins, globulins (antibodies), and clotting factors

Serum

plasma without clotting factors

Granulocytes

neutrophils, eosinophils, basophils, mast cells (cells with visible cytoplasmic granules)

Agranulocytes

lymphocytes and monocytes (lack prominent cytoplasmic granules)

Monocytes

differentiate into macrophages after leaving circulation; primary function is phagocytosis

Neutrophils

most abundant WBC (55–90% of circulating leukocytes); primary function is phagocytosis

Eosinophils

involved in inflammation, allergic reactions, and parasitic infections

Lymphocyte types

B lymphocytes (mature in bone marrow; humoral immunity) and T lymphocytes (mature in thymus; cell-mediated immunity)

Humoral immunity

immune defense using blood and lymph; B cells produce antibodies that neutralize or mark pathogens

Primary lymphatic organs

thymus gland and bone marrow; produce, mature, and release lymphocytes

Secondary lymphatic organs and tissues

lymph nodes, spleen, MALT, SALT, GALT

Spleen and lymph nodes

sites where microbes are encountered and immune responses occur; part of lymphoid tissue network throughout body

MALT

mucosal associated lymphoid tissue

SALT

skin associated lymphoid tissue

GALT

gut associated lymphoid tissue (includes Peyer’s patches)

Peyer’s patches

specific lymphoid structures in the gut (feature of GALT)

Rubor

redness caused by increased circulation and vasodilation

Calor

warmth caused by increased blood flow

Tumor

swelling caused by accumulation of extracellular fluid in tissues

Dolor

pain caused by nerve stimulation from swelling or chemical mediators

Immediate inflammation response

vasoconstriction, blood clot formation, and mast cells release chemokines and cytokines

Cytokines

chemical messengers from WBCs and tissue cells that regulate inflammation, immunity, and cell development

Chemokines

chemotactic factors that attract and guide movement of white blood cells

Vascular reactions in inflammation

vasodilation, increased blood flow, increased vascular permeability, and fluid leakage (exudate formation)

Serous exudate

clear fluid that leaks from blood vessels

Pus exudate

contains cells and debris (including red blood cells and dead material)

Resolution and scar formation

macrophages, lymphocytes, and fibroblasts clean up debris, support repair, and form scar tissue

Diapedesis

movement of white blood cells between endothelial cells of blood vessels into tissues

Fever benefits

inhibits bacterial multiplication; impairs bacterial nutrition; enhances immune response

Phagocytosis

process where a cell engulfs and digests another cell or particle

Steps of phagocytosis

chemotaxis toward bacteria; attachment via receptors/PAMPs; engulfment forming vacuole; phagosome formation; fusion with lysosomes forming phagolysosome; digestion; release of undigested waste

Interferon

protein produced by WBCs and tissue cells; antiviral and anticancer effects; immune enhancer; includes alpha, beta, gamma types; produced in response to viruses and immune signals

Complement system

cascade of serum proteins activated by antigen-antibody complexes or alternative pathways; amplifies immune response; ends in membrane attack complex (MAC); includes classical, lectin (MB-lectin), and alternative pathways

Lysozyme

enzyme found in tears that hydrolyzes peptidoglycan in bacterial cell walls

Defensins

peptides produced by cells and tissues that damage cell membranes and cause lysis of bacteria and fungi