ANSC 3060 Quiz 1 Video 1

Lymphatic & Immune System

functions of the lymphatic system

1. drains excess interstitial fluid from body tissues and returns to circulatory system

2. transports lipids and fat soluble vitamins absorbed through intestines

3. immune response

components of the lymphatic system

lymph

lymphatic vessels

primary lymphatic organs & tissue (immunocompetence) - red bone marrow, thymus

secondary lymphatic organs & tissues (battle grounds) - lymph nodes, spleen, lymphatic nodules (including GALT)

lymph

clear, yellowish liquid derived from intestinal fluid

up to 3 L created daily

mainly water and proteins

interstitial fluid

formed when blood plasma filters out of capillaries; fills spaces between cells

lymphatic capillaries

fluid can come in but not go out

composed of overlapping endothelial cells anchored to tissues

how is lymph circulated?

1. 1-way valves - animal movement squeezes vessels

2. skeletal muscle pump - muscles squeeze back towards heart

3. respiratory pump

lymphoid cells

lymphocytes

macrophages

dendritic cells (APCs)

reticular cells

lymphocytes

protect the body against specific infectious antigens; when activated, they differentiate into powerful immune cells; B cells and T cells

B cells

differentiate into plasma cells which eliminate antigens using protein antibodies (secrete antibodies); stay in bone marrow

T cells

attack and destroy infected cells directly; leave bone marrow and go to thymus for immunocompetence - cells that don’t make it undergo apoptosis

macrophages

generalist phagocytes that eat foreign substances and activate T cells

dendritic cells

capture antigens and present them to the lymphocytes in lymph nodes and elsewhere

lymph nodes

small bean-shaped organs; occur in dense clusters near mammary glands, axillaries, & groin; filter lymph; site of B cell proliferation

label lymph node locations (not in picture - ears)

& parotid - ears

lymph node anatomy

mainly solid - lots of reticular tissue; outer cortex has B cell follicles, inner cortex has T cells in transit

lymph node circulation

1. lymph enters through afferent lymph vessels

2. flows along subcapsular sinuses

3. flows along trabecular sinuses

4. collects in medullary sinuses

thymus

around the heart

1. pre-t cells - more mature than in cortex

2. dendritic cells

3. epithelial cells

4. thymic copuscle - contains regulatory T-cells which prevent autoimmune reactions

spleen

largest lymphatic organ, located below stomach and kidneys

functions:

1. destruction of old RBCs

2. immune response to blood-borne pathogens

3. platelet & macrophage storage

blood supply

1. splenic artery

2. splenic vein

spleen anatomy

very fragile, composed of reticular CT

capsule

trabeculae (muscular)

spleen white pulp

lymph & macrophages; B&T cells (WBCs) proliferate and perform immune functions

macrophages destroy blood-borne pathogens

spleen red pulp

venous sinuses; removal of old blood cells

platelet storage

production of

Gut Associated Lymphatic Tissues (GALT)

scattered throughout connective tissue lining mucus membranes

NOT surrounded by capsule

ex: tonsils, appendix, peyer’s patch (intestines)

lots of lymph in DI tract - food contamination

tonsils

body learns abt pathogens and begins to mount defense/create antibodies for future

peyer’s patches

clusters of lymphoid tissue located in wall of intestine

essential in the immune surveillance of pathogens entering digestive tract

antigen

any substance or organism that provokes an immune response (pollen, bacteria, virus); often proteins

pathogen

disease-producing microbes (bacteria viruses, protozoa, fungi)

resistance

ability to ward off diseases by recognizing the pathogen (looks at part = antigen; pathogen can be antigen)

nonspecific resistance

present at birth, provide immediate but general protection against many pathogens, internal or external

ex: inflammatory response, phagocytes, natural killer cells, antimicrobial proteins

natural killer cells (NK)

attack cells that display abnormal plasma proteins

kill pathogen by releasing perforins or inducing apoptosis

phagocytes

ingest microbes and cellular debris through phagocytosis, two types

1. neutrophils - granular leukocyte

2. macrophages - from monocytes (type of leukocyte); wandering/fixed

inflammation

non-specific defense responsive to tissue damage

symptoms - redness, heat, swelling

1. vasodilation (immediate) - release of substances from damaged tissue increases diameter of arterioles and permeability of capillaries

2. emigration of phagocytes (1 hr+) - diapedesis

diapedesis

process by which white blood cells move out of the capillaries into the surrounding tissue

specific resistance (adaptive immunity)

ability of body to defend itself against specific pathogens

• specificity, memory, systemic

• cell-mediated immune response, antibody-mediated immune response

cellular immunity

t-cells act against target cell

• kill infected cells, release chemicals that enhance inflammatory response or activate other lymphocytes /macrophages

cellular immunity has cellular targets

humoral immunity

antibodies produced by b-cells circulating freely in body fluids, bind temporarily to target cell

• temporarily inactivate

• mark for destruction or phagocytes or complement

humoral immunity has extracellular targets

epitope

reactive region of antigen

antigen receptors

molecules capable of recognizing certain kinds of antigens

antigen receptor diversity

genes determine which foreign substances the immune system will recognize

• cell receptors result of acquired knowledge of microbes likely in environment

lymphocytes make up to a billion different types of antigen receptors

• coded for ~25k genes

• gene segments shuffled by recombination

processing of an exogenous antigen

t-cell types

helper t-cells, cytotoxic t-cells, memory t-cells

helper t-cells

recognize foreign antigens associated with MCH II markers on Antigen-presenting cells (APC)

cytotoxic t-cells

recognizes foreign antigens associated with MHC I markers on infected body cells

kills target cells (with perforin or lymphotoxin)

memory t-cells

remain after cell-mediated immune response with specificity to antigen already encountered

antibody mediated immunity

• b-cells bind to free region

• come antigen taken into cell, combine with MHC II, incorporated into cell membrane

• helper t-cells recognize antigen-MHC complex and costimulate b-cell

• some activated b-cells divide and differentiate into plasma cells

• plasma cells produce antibodies which attack antigen directly

antibodies (immunoglobulins)

glycoproteins that bind with and disable specific antigens; produced by plasma cells

antibody classes

IgG - most abundant in blood

IgA - protects mucus membranes from bacteria/viruses

IgM - found in blood lymph

IgD - found mainly on antigen receptors

IgE - located on cast basophils (least abundant)

ELISA

enzyme-linked immunosorbent assay; test that uses antibodies and color change to identify (ex: SNAP tests, pregnancy test, heart worm/panleuk/parvo tests)

active immunity

results from exposure to the antigen via infection/vax (artificial active imm.)

results in formation of memory B and T cells

effects are long-lasting

passive immunity

results from administration or transfer of antibodies but NOT generation of B or T cells

relatively short lived

ex. colostrum antibody transfer