immune system and lymphatic system Flashcards
role of immune system
to defend the body against infectious microorganisms, pathogenic agents,
noninfectious foreign substances (grafts or tissues coming from other humans/ microorganisms),
transformed cells (cancer cells and any proteins that are produced by the cancer cells)
[body’s defense team.]
it is a morphological counterpart of the immune system.
lymphatic system
consists of:
- cells
- tissues
- organs
(it refers to the physiologic role the chiefly monitors the human body)
what are the 2 immunity that the immune response can be divided into
Nonspecific (innate) immunity:
Represents the first line of defense against microbial invasion.
Consists of:
- Physical barriers (skin & mucous membrane)
*under mucous membrane, we have your lamina propria which prevent foreign materials or foreign organisms from invading the deeper tissues
- Chemical barriers (chemical characteristics of certain tissues
ex: low pH in stomach due to secretion of acidic mol such as hydrogen ions, enzymes, chemicals that digest the food)
- low pH destroy invading microorganisms and prevent opportunistic pathogens from establishing infection in body
- Secretory substances(salivary substances, lysozymes which are enzymes that are encapsulated or stored inside granules of neutrophils )
- Cells of the immune system (pagocyte, monocyte, neutrphil, macrophage, mast cells, basophil and eosinophil, NK cells, gamma delta t cell, dendritic cells) - respond immediately to invadin infections
*JS HRS AFTER ANTIGEN EXPOSURES
Specific (adaptive) immunity:
Precisely targets antigens specific to invader.
Consists of:
-B and T lymphocytes.
(both provide specificity ( highly specific to organism) and immune memory (store memory that has alr been encountered))
they are the chief cellular constituents of lymphatic tissue.
circulating lymphocytes
the 3 major:
- T lymphocytes
- B lymphocytes
- Natural Killer cells.
it refers to the physiologic role the defense mechanism involved in fighting against these foreign material
immune system
*lymphatic system - performs the immune system
briefly explain the division of the lymphatic system
pri lymphatic organs:
thymus
bone marrow
- this is whr lymphocytes r born and educated - production and maturation happens
- learn hot too fight against foreign material
sec lymphatic organs:
lymph nodes & vessels
- serves as connecting framework for the lymphatic or lymphocytes to travel the whole body
*both lymphatic organs r usually connected to the lymphatic vessels
difference between B and T lymphocytes
B lymphocytes:
humoral immunity
- immune response in an adaptive immune response
- mediated by proteins (antibodies)
[role of antibodies
- coat and neutralize invaders
- serve as markers for other immune cells]
- antibodies are produced by mature B lymphocytes, specifically plasma cells
T lymphocytes:
cell mediated immunity/ cell mediated response
- directly kill/ respond to the cells that has been infected by foreign microorganism
- does not produce any antibodies but can recognize this foreign material (MHC, major histocompatibility complex)
they differentiate in the thymus and account for the majority of circulating lymphocytes
T lymphocytes
(account 60-80% of circulating lymphocytes)
- comes from the common lymphoid progenitor (CLP) from the bone marrow
- however once they mature into a common lymphoid progenitor, it travels to the thymus for differentiation into T lymphocytes
how are T lymphocytes subclassified according to the presence or absence of two other important surface markers
*CD stands for clusters of differentiation
🔹 1. Helper T Lymphocytes (CD4+ T cells)
help activate other immune cells. divided into three main subsets based on the cytokines they produce and their specific roles:
➤ Th1 cells
Produce: Interferon-gamma (IFN-γ)
Function: Activate macrophages to destroy ingested microbes.
➤ Th2 cells
Produce: Interleukins 4, 5, 10, and 13
Function:
- activate eosinophils, basophils, and mast cells
- fight parasitic infections
- allergic responses
➤ Th17 cells
Produce: Cytokines (chemokines)
Function: Recruit neutrophils to the site of infection, especially against fungi and bacteria
🔹 2. Cytotoxic T Lymphocytes (CD8+ T cells)
killer T cells that destroy infected or abnormal cells.
Recognize and kill cells presenting specific foreign antigens (like virus-infected or cancer cells)
Mechanism of killing:
- Release perforins (form pores in target cells)
- Release granzymes (enter through pores and induce cell death)
Function:
- Eliminate infected cells
- Reject transplanted (foreign) tissues
🔹 3. Regulatory T Lymphocytes (Tregs)
help control and regulate the immune response to prevent overactivity.
Markers: Express CD4+, CD25+, and FOXP3
Are a diverse subset of CD4+ T cells
Functions:
- Suppress the activity of other T lymphocytes
- Inhibit helper T cells from releasing cytokines
- Prevent maturation and activation of cytotoxic T cells
- Help maintain immune tolerance (preventing autoimmunity)
it serve as peptide display molecules for recognition by T lymphocytes
briefly explain the 2 types
Major Histocompatibility Complex (MHC) molecules
- once detected by the T cell receptors, foreign materia will be destroyed
1 MHC I
- expressed on the surface of all nucleated cells and platelets.
2. MHC II
- expressed on the surface of all APCs (hence directly attacked by helper t cells specifically)
- critical in immune interactions
it differentiate in the bursa-equivalent organ and participate in humoral immunity
B lymphocytes
- production of antibodies, also called immunoglobulins (Ig)
- the immune protein associated with humoral immunity
*bursa-equivalent organ is the bone marrow
*humoral immunity aka antibodies (immunoglobulins)
[Bursa-Equivalent Organ:
In birds, B cells mature in the bursa of Fabricius.
In humans (and other mammals), this organ doesn’t exist, so the bone marrow serves as the bursa-equivalent, meaning B cells develop and mature there.]
briefly explain the different antibody classes in humans
[G, M, A, D, E]
- antibody percentage in the plasma
- presence in the psites other than blood, CT and lymphoid organs
- known functions
percentage (%):
IgG - 75-85 MONOMER
IgM - 5-10 PENTAMER (has 10 antigens and its the largest)
IgA - 10-15 DIMER WITH J CHAIN AND SECRATORY COMPONENT
IgD - 0.001 MONOMER
IgE - 0.002 MONOMER
sites:
IgG - fetal circulation in preggy
IgM - B lymphocyte surface (as a monomer)
IgA - secretions saliva, milk, tears
IgD - surface of B lymphocytes
IgE - bound to surface of mast cells and basophils (these creates this specific Ig to neutralize and destroys )
known functions:
IgG -
activates phagocytosis
neutralize antigens
IgM -
first antibody in initial immune response
activates complements
IgA -
protects mucosae
hence, important to breastfeed babies as it wi build their immune system
IgD -
antigen receptor triggering initial B cell activation
IgE -
destroys parasitic worms and participates in allergies
it is part of innate immunity, but share similarities with adaptive immunity as they are specialized to kill certain types of target cells
briefly explain its function
NK cells
- Programmed to recognize transformed cells through natural cytotoxicity receptors. After recognition, NK cells directly eliminate these cells by releasing perforins (enzymes that r pore-formers that facilitates the formation of pores in infected cells = increase permeability - apocytosis) and granzymes (stimulate production or activation of enzymes caspaces).
- Can kill cells indirectly by secretion of pro-inflammatory cytokines, and perform antibody dependent cell-mediated cytotoxicity.
it interacts with helper CD4+ T cells to facilitate immune response.
Antigen-presenting cells (APCs)
what system does APCs belong to
mononuclear phagocyte system:
- Macrophages
- Kupffer cells (liver)
- Langerhans cells (epidermis)
- Dermal macrophages (dermis)
- Dendritic cells (lamia propria)
what are the other APCs that do not belong to the MPS
B lymphocytes
type II and III epithelioreticular cells
- involved in thymic education
how does t lymphocytes responds to other type of cells
Cytotoxic (CD8+) T Cell
Main Role:
Kill infected or abnormal cells
Recognizes Antigen Presented By: MHC Class I molecules
Activation Requirements:
1. Antigen + MHC I recognition
2. Co-stimulation via B7–CD28
Killing Mechanism:
Perforins and Granzymes
Target Cells:
virus-infected cells
cancer cells
foreign tissue grafts
this can recognize the specific type of major histocompatibility complex
CD4 and CD8
CD8+ - only recognizes the MHC1 CD4+ - only recognizes the MHC2 mol.
*this specificity is impt to regulate the activity of the T lymphocytes so that they can be
what are the 2 types of cells that B lymphocytes can mature to
- plasma cells
- directly produce antibodies - memory B cells
- which are the cloned version of the B lymphocytes
- exposed to certain characteristics f foreign material
activation of B lymphocytes
- Antigen Binding
Antigen binds to B cell receptor (BCR) on the surface - Internalization & Presentation
B cell presents antigen via MHC Class II - Co-stimulation
CD4+ T cell binds to MHC II + TCR and provides help - Full Activation
B cell becomes plasma cell (makes antibodies) or memory B cell
It proliferates to make more copies
*soluble B cell receptors - soluble in blood
appearance of the antibody
y-shaped
- consists of FC fragment and antigen binding site or FAB fragment
- each protein of antibody or immunoglobulins has 2 antigen binding site (bind to foreign material)
- FC fragment can bind to compliment
composition of lymphatic tissue
lymphatic tissues and organs:
Lymphatic vessels
Diffuse lymphatic tissue and lymphatic nodules
Lymph nodes
Thymus
Spleen
are the route by which cells and large molecules pass from the tissue spaces back to the blood.
Lymphatic vessels
- begin as networks of blind capillaries in loose CT (areolar tissue - interspersed with blood capillaries)
it is produced from interstitial fluid that enters the lymphatic capillaries
lymph
- present in the tissue
- composition: same w plasma from the blood
where does the lymphocytes circulate
through both lymphatic and blood vessels
- lymphocytes conveyed in lymph enter lymph nodes via afferent lymphatic vessels
- it conveyed in blood enter the node through the walls of high endothelial venules, HEV
it is accumulations of lymphatic tissue found in alimentary canal, respiratory passages, and genitourinary tract
diffuse lymphatic tissue
- aka as MALT
- found in the lamina propria (loose CT of mucosa)
they are discrete concentrations of lymphocytes contained in a meshwork of reticular cells.
Lymphatic nodules
lymphatic nodules consiting of small lymphocytes is called pri nodules
what are the distinctive features of the Secondary lymphatic nodules
Germinal center
- lighter stain portion of sec lymphatic modules
- characterized by the presence of actively proliferating B lymphocytes
- exposed to antigen
Mantle zone or corona
- composed of naive lymphocytes (not yet exposed to any antigens)
where are lymphatic nodules usually found
in structures w alimentary canal:
tonsils
peyer patched
vermiform
appendix
form a ring of lymphatic tissue at the entrance of the oropharynx
tonsils
types:
Pharyngeal tonsils - aka adenoids
Palatine tonsils - aka tonsils
Lingual tonsils - base of the tongue
they are located in the ileum and consists of numerous aggregations of lymphatic nodules containing T and B cell
Peyer’s patches
it arises from the cecum. The lamina propria is heavily infiltrated with lymphocytes and contains numerous lymphatic nodules.
Vermiform Appendix
- highly present during the newborn stage and when newborn matures into a child
*its gone once reaches adult
*studies have made that appendix is a major lymphatic tissue which involves the immune system of the gut
it filter lymph along the pathway of
lymphatic vessels and initiate adaptive immune responses to antigens
Lymph nodes
- present in whole body but high no. in neck, axilla and groins, mesentery
supporting elements of lymph nodes:
Capsule (dense CT that covers the lymph nodes)
Trabeculae
Reticular tissue (framework)
it contains several types of cells that perform different functions in generating immune responses.
the reticular meshwork of the lymph nodes
diff cells:
1. Reticular cells
synthesize and secrete type III collagen (reticular fibers) and the associated ground substance.
- Dendritic cells
bone marrow-derived APCs.
present antigens to T cells
bone marrow derived antigen presenting cells
express high levels of MHC2 molecules - Macrophages
phagocytic cells and APCs.
contain both MHC1 and MHC2
- MHC2 higher in conc. of dendritic cells compared to macrophages - Follicular dendritic cells (FDCs) have multiple, thin, hair-like branching cytoplasmic processes where the antigen-antibody complexes adhere.
- traps antigens
General Architecture of Lymph Nodes
- Cortex
- Superficial (modular) cortex
lymphatic nodules present
- Deep cortex (paracortex)
T cells present
*development paracortex is highly dependent on the thymus
aka thymus-dependent cortex - Medulla
- Medullary cords
- Medullary sinuses
lymph travels here
follicular dendritic cells traps antigen that comes from the lymph
a bilobed lymphoepithelial organ located in the superior mediastinum.
thymus
- normally undergoes involution during puberty
(SIZE OF THYMUS DECREASES AS WE AGE)
The primary organ in which T cells emerge
Thymus
General Architecture of Thymus
thymus possess a thin connective tissue capsule from which trabeculae extend into the parenchyma.
The thymic parenchyma contains developing T cells in an extensive mesh work formed by epithelioreticular cells.
6 types of epithelioreticular cells in the thymus:
IN CORTEX
Type I:
serve to separate the thymic
parenchyma from the connective tissue of the organ.
high no. of occluding junctions - separation barrier btwn CT
Type II:
compartmentalize the cortex into isolated areas for developing T cells.
high no. of desmosomes - serve as localized anchors for neighboring cells
cellular framework for the developing T cells
Type III:
create a functional barrier between cortex and the medulla.
high no. of occluding junctions - serve as barriers
!!TYPE 2 AND 3 = has MHC1&2 MOLECULES!!
IN MEDULLA
Type IV:
in cooperation with type III, also forms a barrier at the corticomedullary junction.
high occluding junctions
Type V:
compartmentalize groups of lymphocytes at the medulla.
high no. of desmosomes
Type VI:
form the most characteristic feature of the thymic medulla, the Hassall corpuscles. (HC contains keratin granules which aka keratohyalin granules)
- developed from the oropharyngeal epithelium
it is where thymocytes must pass two sequential life and-death tests to survive.
briefly explain the 2 steps
Thymic Cell Education
- approx 98% of T cells are degraded/ did not pass this process
- approx 2% become helper T cells and cytotoxic T cells
2 steps:
1. Positive Selection:
Survival dependent on ability to bind to MHC molecule.
when the T cell mature, it will exhibit CD4 and CD8 - called double positive stage
- Negative Selection:
Survival dependent on not recognizing self- antigen
Self-tolerance: ability of the immune system to not affect the self antigen present - in order to inhibit autoimmune responses
It is about the size of a clenched fist and is the largest lymphatic organ. Located at the upper left quadrant of the abdominal cavity and has a rich blood supply.
spleen
- filters blood and initiates adaptive immune responses to blood-borne antigens.
briefly explain the 2 splenic plup
White pulp:
- consists of a cylindrical mass of
lymphocytes arranged around a central artery, and splenic nodules.
Red pulp:
- contains large numbers or RBCs
that it filters and degrades. (contains splenic sinuses separated by cords of Billroth.)
an endothelial cells that line the splenic sinuses
stave cells
- extremely long
- contain actin filaments that can contract (control the passage of blood)
in the arteries, RBC are ejected towards the splenic cord
summary of lymphatic organs
refer to table
it is the first immunoglobulins that usually encounter
IgM
- as they are involved in the early response of the immune system towards the invading microorganisms
if IgG- and IgM+ = infection started
if IgG+ and IgM- = no current infection but patient has past infections
where are reticular fibers present
bone marrow
lymphatic tissue
associated ground substance
