Lesson 1.1 Basic physiology immune system Flashcards
What are the two general means of protection the body uses against infection
- Physical barriers: skin, epithelial surfaces, cilia
2. Chemical barriers: acids, mucous, lysozymes
What are the two components of immunity
Innate immunity and adaptive immunity
What are the primary lymphoid tissues
Bone marrow and thymus
What are the secondary lymphoid tissues?
Lymph nodes, lymph nodules, lymph vessels, spleen
What are the primary (central) lymphoid tissues “organs” where immune cells mature
Red bone marrow: Pluripotent stem cells give rise to all of the different types of blood cells, including all immune cells (“leukocytes” or white blood cells)
Thymus gland above the heart in the thorax, site of T lymphocyte maturation
The site where T lymphocytes mature and develop “self-tolerance” before participating in immune reactions
Thymus
Purpose is to promote efficient interactions between antigens and immune cells and a controlled environment in order to maximize the rapid development of immune responses
Secondary Lymphoid tissue
along lymphatic vessels, to process antigens found in interstitial fluid
Lymph nodes
Process antigens found on mucosal surface. Include tonsils and adenoids in pharynx, Peyer’s patches )
Lymphoid aggregates in the appendix, and other diffuse lymphoid aggregates in the esophagus, on other mucosal surfaces
Lymph nodules
Process antigens found in the blood
Spleen
Large numbers of lymphocytes and macrophages are exposed to antigens as they flow around the WBC contained in the lymph nodes / lymph nodules / spleen
Secondary lymphoid tissues
Drains tissue fluid, cells and antigens from most tissues, through lymph nodes and back into blood via thoracic duct
The lymphatic vasculature
Lymphoid tissue associated with mucosal surfaces (MALT)
Associated with gastrointestinal tract, respiratory tract, breast, urogenital tract (i.e., all mucosal tissues)
Has epithelial covering with specialized phagocytic epithelial cells (M cells) that transfer antigen into the lymphoid tissue. Secrete IgA onto mucosal surface – initiates inflammatory reaction and prevents microbial binding to surface
Lymph nodules
Functions as a filter for antigens in the blood, a site for immune reactions, location where old or damaged RBC and platelets are removed, and as a storage organ for erythrocytes
Spleen
what happens if the connective tissue capsule surrounds the spleen rupture?
“Ruptured spleen” and significant abdominal bleeding
what are the two distinct components of the spleen
Red pulp and white pulp
Red pulp
Contains large numbers of blood-filled small diameter sinusoids (causes lysis of old RBCs), site for removal of old and damaged RBC by macrophages
White pulp
Contains WBC necessary for immune response (lymphocytes, macrophages). Responsible for the immunological function against antigens carried in blood. It enlarges with immune reaction (e.g., results in splenomegaly with infectious mononucleosis)
Lymphocytes
T and B lymphocytes Natural killer (NK)
Granulocytes
Basophils / mast cells
Neutrophils
Eosinophils
Give rise to “plasma cells” which secrete immunoglobulins (antibodies – “Humoral” ) and leave the bone marrow fully mature
B lymphocytes
Secrete cytokines which act on other immune cells (CD4+, helper). Cause lysis of infected cells (CD8+, cytotoxic) “cell mediated”. Release by bone marrow and must undergo further maturation in the thymus gland
T lymphocytes
Lymphocytes (T and B cells) Make up ______of blood leukocytes
(WBC)
20-35%
Antigen presenting cells
variety of cell types including: Monocyte / macrophages/ dendritic cells. Make up 1 – 6% of WBC in blood Specialized names: Langerhans cells / dendritic cells (skin). Microglia (CNS). Kupffer cells (liver
Serve a variety of functions in the immune response: Phagocytosis to eliminate microbes, inanimate “particles” Secretion of cytokines (IL-1, IL-6, TNF) to communicate with other WBC
“Antigen presentation” necessary for lymphocyte reaction to specific antigens (adaptive immunity)
Antigen presenting cells
Circulate in blood for ~1 day (2-8% of WBC) and are the largest leukocyte and mature into macrophages when they migrate into the tissues and acquire greater phagocytic ability
Monocytes
Engulf and kill invading microorganisms and infected cells, clean up dead cells and cellular debris. Help induce/maintain inflammation by secreting signaling proteins (cytokines) to activate and recruit other immune cells
Macrophages
Primary role is phagocytosis of bacterial invaders/destroyed or removed innert materails. Most abundant leukocytes (50-70% of WBC). 1st to arrive at the site of acute inflammation- can form pseudopods and are highly mobile
Neutrophils
Engulf & destroy bacterial invaders using degradative enzymes (lysozymes) and antimicrobial substances in their cytoplasmic granules, including H2O2 and NO
Neutrophils
1-3% of WBC. Kills parasitic worms. Recruited to sites of acute inflammation. Longer life span than neutrophils. Involved in chronic inflammation. Granules contain digestive enzymes, lysozyme, peroxidase, & inflammatory chemicals. Key component of allergic asthma & other allergic reactions
Eosinophils
Certain uncommon “eosinophilic” inflammatory conditions, e.g., eosinophilic esophagitis, eosinophilic neuritis
Neutrophils
Found in blood (rarely seen, < 1% of blood WBC)
Mast cells are very similar to basophils, fixed in tissues
Both are non-phagocytic cells which, when activated, release compounds from cytoplasmic granules (including histamine)
They play a major role in allergic responses, particularly type I hypersensitivity reactions (classic allergy)
Basophils
Both are non-phagocytic cells which, when activated, release compounds from cytoplasmic granules (including histamine) and play a major role in allergic responses, particularly type I hypersensitivity reactions (classic allergy)
basophils and mast cells
Very similar to basophils, fixed in tissue first line of defense along mucosal surfaces
Mast cells
Antigen
large proteins with high molecular weight (~10,000 or 65 AA) Substance that can be recognized by an immune system as foreign (“non-self”) and provoke an immune reaction (virulence)
Autoantigen
Self”-molecules that inappropriately provoke an immune reaction
Allergens
Are antigens that provoke a hypersensitivity response (allergic response) to otherwise non-harmful antigens
Epitope
Small part of an antigen that interacts with a specific immune antigen receptor (antibody, cell surface receptor). Any antigenic protein may have multiple epitopes in its structure. Each epitope is recognized by a different, specific antibody or immune cell antigen receptor
highly conserved throughout nature as they are molecular patterns essential to the normal function and effectivity of microbes
Pathogen-Associated Molecular Patterns (PAMPs)
Cannot evade immunologic detection (> 103 patterns recognized)
Examples include: Nucleic Acids: ssRNA, dsRNA (virus); CpG islands (virus, bacteria)
Proteins: pilin and flagellin (bacteria).
Cell wall lipids: lipopolysaccharide (gram-neg. bacteria); lipoteichoic acid (gram-pos. bacteria). Carbohydrates: mannan (fungi, bacteria); dectin glucans (fungi)
PAMPs (pathogen associated molecular patterns)
Molecular patterns expressed on the surface of stressed, diseased, injured cells that serve as markers to signal destruction
Danger (Damage)-Associated Molecular Patterns (DAMPs)
Examples of DAMPs
Heat shock protein, HSP; alterations in phospholipid structure; nuclear tags
Are recognized by Pattern Recognition Receptors (PRR): on phagocytes (Toll-like receptors) – leads directly to phagocytosis and in serum (opsonins) – lead to complementation and signaled for phagocytosis
PAMPs and DAMPs
Initiate the innate immune system
Pathogen-Associated Molecular Patterns (PAMPs) and Danger (Damage)-Associated Molecular Patterns (DAMPs)
Diverse group of small soluble signaling molecules secreted by cells of the immune system.
Either fight the microbe directly or mobilize the immune system against the microbe
Promote inflammation, target cell growth/survivability/maturation or it’s activation/suppression
Cytokines
Most act in a paracrine fashion; some are autocrine (T/B-cell differentiation) or even endocrine (IL-1 and TNF⍺ induce fever)
Cytokines
