Immune system and immunity

THE IMMUNE SYSTEM and IMMUNITY

Immune System

a biochemical complex that protects the body against pathogenic organisms and other foreign bodies.

The structure, cells and soluble constituents that allow the host to recognize and respond to foreign stimulus.

Primary Role of The Immune Syatem

Surveillance and destruction of substances that are foreign to the body.

- bacteria, viruses, parasites or fungi

Primary Function of the Immune System

1. To protect the body against invasion by so called non-self substance.

(any and all substances that are considered “foreign”)

2. To differentiate between “self” and “non-self” and to destroy that which is “non-self”

Origin, Destination and Structure of the Cells and

Tissues

Bone Marrow

constitutes almost 5% of the total body weight and is responsible for the formation of all blood cells in adult

Stem Cells

all cells originates from undifferentiated pluripotential hemopoietic stem cells, which can be found first in the mammalian embryo with in the liver then the spleen.

are pluripotential CD34+

Erythropoiesis occurs when a CFU-S cell gives rise to

burst-forming units-erythrocytesgranulocytopoiesis

the generation of three types of granulocytes

monocytes more pathogenic than neutrophils or

eosinophils

Dendritic Cells

are bone marrow derived cells specialized for presenting antigens to either CD4+ or CD8+ t cells in order to initiate a primary immune response.

Thymus

is a primary lymphoid organ that is required for the generation of immunocompetent CD3+4+ & CD3+8+ cells necessary for an adaptive immune response.

Lymph Nodes

are encapsulated structures that are strategically placed throughout the body to receive and filter antigens & cells from peripheral interstitial fluid and lymph.

Localization of Cells

1.Superficial cortex containing primary & secondary

follicles with germinal centers containing dark and light zone

2. Deep cortex containing high endothelial post-

capillary venules

3. Medulla with medullary cortex

Spleen

is an encapsulated organ with lymphoid tissue called white pulp(WP), which can respond to blood-borne antigens surrounded by the red pulp(RP).

Mucosal Associated Lymphoid Tissue (MALT)

T Cellsabout half of the stem cells

migrates to the thymus gland where they differentiate into T lymphocytes or T cells

small lymphocytes found in the blood

about 70%-80% of the lymphocytes in peripheral blood are T cells.

Two immunologic Functions of T cells

1. Effector includes the cytolysis of virally

infected cells & tumor targets & the production of lymphokines

2. Regulator includes the ability to amplify or

suppress other effector lymphocytes

Most of the T-cells express three of the following CD

Markers

CD2 CD3CD4CD8

Two Subpopulation of T cell in the Circulation

1. Those with CD2, CD3, CD4 phenotype

2. Those withCD2 ,CD3, CD8 phenotype

includes:1. Helper T cells (Th cells)2. Suppressor T cells ( Ts cells)3. Cytotoxic T cells (Tc cells )4. Delayed hypersensitivity T cells (Td

cells)

B cells

Other lymphocytic stem cells differentiate in the liver & intestinal lymphoid areas into B lymphocytes or B cells.

About 10%-15% of the lymphocytes in peripheral blood are B cells.

Each is capable of producing hundreds of specific antibodies per second

IMMUNITY

in positive sense: providing natural resistance,

recovery, and acquired resistance to infectious disease.

in negative sense: may result in rejection of a life-saving

transplant

Types of Immunity

Natural or Innate

present at the time of birth or that develops during maturation

- refers to anatomical, cellular, and humoral defenses that function in the early stages of host defense response to foreign substances (antigens)

- cells that function in innate immunity does not possess immunological memory.

- they are nonspecific because the cells do not express receptors specific to one particular antigen.

Acquired or Adaptive

which is acquired as a result of prior experience with a foreign substance

Further divided into:humoral immunity (gut associated tissue GALT)

is mediated by the antibody secreted by terminally differentiated B cells, the plasma cells

Type I, II, III hypersensitivity reactions

Cell mediated immunity (Thymus) involves T cells that recognize antigen in an

MHC-restricted fashion(CD4 - T-helper cells, CD8 - T-suppressor cells) tissue graft rejection, delayed hypersensitivity

reaction, mononuclear inflammatory reaction

Characteristic of Natural Immunity

1. Do not possess immunologic memory2. Non specific

• operates as the first line of defense against pathogens

includes the Physical barriers:– Skin– Mucous membrane– Susceptibility & nonsusceptibility– The provision of an unfavorable environment

for the infecting organism

Host defense in Innate Immunity

1. Cells antigen presenting cells basophils eosinophils mast cells natural killer cells

phagocytes

2. Humoral Factors complement proteins lactoferrin (present in tears, sebaceous & sweat

glands)

lysozymes

3. Anatomical Barriers cilia mucus membrane skin

4. Resident Flora mainly nonpathogenic bacteria prevents colonization of new

microorganisms.(intestine, vagina & nasopharynx)

Other factors that forms the overall action of innate

immunity

1. Inflammation

2. Complement

3. Phagocytosis

Adaptive immunity

1. Acquired adaptive immunity is highly specific, inducible, discriminating

& unforgetting. - cell surface receptors are specific for a particular

antigen. - memory because lymphocytes that have been

activated in response to a particular antigen will respond much faster in a subsequent exposure to the same antigen.

T lymphocyte dependent response.

TwoTypes of Adaptive immunity

1. Acquired active immunity by actual infection or inoculation that

causes the production of specific protective antibodies

(vacines - hepatitis, tetanus)

2. Acquired passive immunity afford temporary protection against

invading antigen. (RhIg given during birth, HBIg)

Characteristic of Adaptive Immunity

1. With Memory

2. Specific

Host Defense in Adaptive immunity

1. Cells B cells plasma cells T cells (cytotoxic & helper cells)

2. Humoral factors antibodies cytokines

Factors involved in the degree of infection

size of infecting dose

route of administration

type of infective agent

Nothing is predestined: The obstacles of your past can become the gateways that lead to

new beginnings.

Thank you and God bless!!!