general functions of the immune system

1. involvement in immune disorders
2. development of vaccines
3. emergence of AIDS
4. barrier to organ transplants-rejection of "non-self" cells and tissues
5. stimulation or the immune system to battle cancer

1. innate (natural)
2. adaptive (acquired)

both defenses are supplied by host

1. innate immunity

an initial and quick response "first responders"

-designed to block invaders at the tissue level

develops later, develops slowly over time

-provides long-term protection, production of "memory"

1. have progenitor cells (ancestral cells) 
2. hematopoesis

 an extra set of cells that can be called on at anytime

have the ability to develop into any type of cell

(embryonic cells)

1. erythroid pathway
2. lymphoid pathway
3. myeloid pathway

-develop into b-lymphocytes, t-lymphocytes, Natural Killer cells

(b-cells, t-cells, NK cells)

-leukocytes (WBCs)

-includes neutrophils, eosinophils, basophils, monocytes, mast cells, megakaryotes, dendritic cells

1. Lipid (fat) cells
2. Fibroblasts
3. Endothelial cells
4. Macrophages

-epithelial cells that line blood vessels

-importance is mechanical movement or immune cells from blood to tissues

-provide substance that prvents clotting

-division product of monocytes

-phagocyte cells and debris also stimulata lyphocytes

-it is the connective tissue of organs

-site where the bone (refered to as a tissue) and thymus are tissues where blood cells develop and mature

1. GATA II
2. Ikaros
3. BMI 1

involved in development of all lineages

(all -phoids:lymph-, myl-, eryth-)

1. programmed cell death (apoptosis)
2. necrosis
3. life span

-planned cell death=orderly process of eliminating cells

-involves chromatin condensation, nuclear fragmentation (pyknosis), changes in the cell memmbrane and phagocytosis of the end products

-Blebbing (compartimentation) of the cell

-important in cell elimination and embryonic development

-1 day to 20-30 years

-hence the need for an orderly process of removal

1. Lymphocytes
2. Antigen presenting cells (APCs)
3. Effector cells

a. B-cells

b. T-cells

c. NK cells

a. dendritic cells

b. follicular dendritic cells

c. macrophages

a. T-cells

b. macrophages

c. granulocytes

a. eosinophils

b. neutrophils

c. basophils

-produce specific receptors for antigens, hence they are mediators of adaptive immunity

-receptor ligand binding triggers cellular response (signal cascade)

-generally look the same but have very different lineage, function, and phenotype (physical manifestiation)

-distinguishable by cell surface proteins indentified by a system called Cluster of Differentiation (CD)

-helper T-cell (CD4⁺)

-T-cytotoxic Lymphocytes (CTLs)(CD8⁺)

-originally identified on WBCs

-functions include: receptors, signaling, cell adhesion

-system of CDs originated from Paris in 1982 @ HDLA conf

-350+ in existence

-antibodies that are tagged with fluorescencent capability will determine preference and # CD specific cells by using flow cytometry

-in mammals the site of development and maturation is in the bone marrow

-originally called B-cells because they were discovered in birds bursa of fabricius(like thymus)

-mature B-cells display antibody receptors for antigen

a) effector B's which perform a specific function in response to AB

b) plasma cells which produce secreted antibody

c) Memory B's which are the same as other B's but live longer

• generated in bone marrow
• mature in thymus
• express T-cell receptor on their surface

• T-cells only recognize antigen or foreign body bound to a protein found on the surgace of other cells called Antigen Presenting Cell (APCs)

the APCs present antigen to T's bia the Major Histocompatibility Complex (MHC)

-

Class I is presented of all nucleated cells of vertebrates

Class II is expressed on only a few specialized APCs

Class III is involved in the production of Compliment

1. T_H(T-helper)-function to help B-cells produce antibodies and help phagocytes destroy inested antigens

2. TCLs(T-cytotoxic lymphocytes)- kill of lyse cells that contain microbes

• some refer to them as a sub-pop'n of T-cells
• large granular lymphocytes, because they release small cytotoxic granules that cause the cell to die by apoptosis of necrosis
• cytotoxic aganst tumor cells and virus infected cells

• start out as monocytes in blood then differentiate and mature into macrophages
• development=1st in bone marrow as promonocytes then monocytes then tissues
• in tissues macrophages enlarge

-specific name depends on which tissue they reside

1. intestinal-gut
2. alveolar-lung
3. histocytes-CT
4. kupffer cells-liver
5. mesangial cells-kidney
6. microglial cells-brain
7. osteoclasts-bone

• versitile
• sense pathogens and serve as initial stimulus for inflammation
• they do this by secretion of interleukins and TNFα which is a cytokine that recruits neutrophils to site of infection
• secrete cytotoxic proteins
• phagocytize microbes
• play a role in tumor eradication

umbrella term for secreted proteins involved in innate and adaptive immunity

• in innate macrophages produce cytokines
• in adaptive T-cells produce cytokines

• a rxn of the inate immune system to many factors
• can be acute(tissue injury) or chronic(wasting disease)
• has an accumulation of WBCs and proteins at the site of inflammation(can be infection, toxic exposure, or cell injury site)
• is initiated by changes in blood vessels and those changes allow cells and proteins to travel to the site of inflammation
• vascular dialation causes redness

process is called leukocyte extravasation

4 steps:

1. rolling of cells
2. activation by chemoattractant
3. adhesion and arrest
4. transendothelial migration(diapedisis-leukocytes travel from vessels to tissues)

-once the cells reach the inflammation site they release more chemoattractants calle chemokines

based on morphology and staining, they have a granular appearance

1. neutrophils
2. eosinophils
3. basophils

• multilobed nucleus
• stain with acidic and basic stains
• aka Polymorphonuclear Leukocytes (PMNs)
• first to arrive at a site of inflammation
• increase of curculative neutrophils indicates some sort of infection
• phagocytic and generate reactive O₂ species

• bi-lobed nucleus
• stain eosin red(appear bright orangy/pink)
• phagocytic
• invilved in defense against pafasites and also involved in allergy

• have a kidney shaped nucleus
• stain bluish-purplish(methylene blue)
• not phagocytotic
• major role in allergic response by degranulating to release

• act against parasites and pollen
• play a major role in hypersensitivity
• is immediate, causes vascular permeability which causes lung and intestinal muscle contractions

• major cells involved in hypersisitivity
• derived from bone marrow
• locate in tissue next to BV
• binding of antibody to mast cells with antigen causes the release of cell contents

[image]AB-AG complex  »»  mast cells »»  release of cell contents which causes inflammation

• 1^st immune cells discovered
• resemble dendrites of nerve cells
• many types depending on the tissue: nose, stomach, lungs, intestine, areas of contact of antigen

• not related to dendritic cells
• reside in follicles of lymph nodes
•  present in-tact antigen to B-cells for B-cell activation which then divide to produce antibody

Primary

bone marrow

thymus

Secondary

lymph nodes

spleen

MALT

(mucosa assoc. lymphoid tissue)

Types of  MALT

(ALT=Associated Lymphoid Tissue)

1. GALT-gut
2. BALT-bronchi
3. NALT-nasal cavity
4. LALT-larnyx
5. SALT-skin
6. VALT-vascular system
7. CALT-conjunctiva of the eye

• vessels that collect tissue fluid and return it to the blood
• also includes lymph organs that receive lymph(fluid)
• lymph is moved around the body by limb movement through one-way valves »» excersice moves lymph back to heart »» lymph transports antigens around the body
• leakage of valves causes fluid accumulation=edema
• lymph transports immune system cells through lymph nodes

• site of T-cell maturation
• flat, bilobed, located, above heart
• surrounded by a capsule and subdivided further into lobules
• has cortex(outer region) and medulla(inner region that contains immature T-cells)
• receptors on T-cells interact with APCs that present antigen via MHC
• tissue, with age, is replaced by fat
• T-cells here that overreat may cause auto-immune disease

• complex site of hematopoesis and fat deposition
• cells move from bone marrow to blood to tissues/organs
• B-cells of bone marrow are responsible for 90% of IGG and IGA(antibodies in plasma)

• interspersed throughout body
• surrounded by a capsule(distinguishes them from MALT tissue)
• has 3 regions: cortex, paracortex, medulla
• in lymph, dendritic cells pick up antigen and transport to lymph nodes

• has regions called lymphoid follicles
• in the medulla there are areas called sinusoids (areas where lymph perculates through)

• abdominal organ
• unique because it mounts an immune response to antigens in blood
• filters blood and traps antigens
• not supplied by lymph
• also surrounded by a capsule
• also has sinusoids
• inner regions are divided into red pulp and white pulp

red pulp- where old and defunct RBCs are destoryed

white pulp- rounded areas mostly pop'd by T-cells 

         white pulp possesses a center area of B-cells                   (when antigenically stimulated the germinal layers will stain lighter)

• lymphoid cells are not encapsulated(no boundary)-continuous with other tissues in area
• found in areas under the skin(cutaneous) and in respiratory tract and gastrointestinal tract(mycosal)
• tonsils and Peyer's patches are mucosal

• located under the surface of the GI tract
• found mostly in the ileum of small intestine
• appear like lynphoid nodules just under GI epithelium

1. palantine-located on left/right of the back of the throat
2. lingual-on back of tounge
3. pharyngeal-(adenoids) located where nose meets mouth