Immunology Immunology

Immune system of organism. Immune system of organism. Antigens Antigens

Features of immune system Features of immune system

Situated in different parts of bodySituated in different parts of bodyRapid regeneration Rapid regeneration Circulation of immune cells in the Circulation of immune cells in the

organism organism Possibility to “learn” Possibility to “learn” Possibility to form a lasting memory Possibility to form a lasting memory

General components of immune General components of immune systemsystem

Immune system consist of:

Central organs:

Thymus

Red marrow bone

Peripheral organs

Spleen

Tonsils

Network of lymph nodes

Lymphatic of intestine

Appendix

Red marrow bone Red marrow bone

Function:

Production of blood cells (hemopoesis)

Maturation of B cells

The thymus glandThe thymus gland

Functions:

Differentiation and maturation of T-lymphocytes

Synthesis of hormones (thymosin, thymolin) that influence to lymphocytes in blood stream.

Lymph node Lymph node

Contain T-lymphocytes and B-lymphocytes

Functions:

filtration of particulate materials (microbes) and contribution of lymphocytes to the lymph as it passes through.

Spleen Spleen

Functions:

Phagocytosis of foreign matter

Immune reactions against bacteria

Removes and breaks down worn erythrocytes

Blood cell development (1)Blood cell development (1)

Blood cell development (2)Blood cell development (2)

Major circulating blood cells of the Major circulating blood cells of the bloodstream bloodstream

Dispedesis and chemotaxis of Dispedesis and chemotaxis of leukocytesleukocytes

Major stages in the development of B Major stages in the development of B and T cellsand T cells

Maturation of lymphocytesMaturation of lymphocytes

Parts of specific immunityParts of specific immunityThe humoral immune system involves the antibodies that are dissolved in the body fluids such as the blood, lymph, and mucus secretions

The cell-mediated immune system involves lymphocytes known as T cells, they act directly on other cells. It is most effective against intracellular pathogens and eukaryotic agents

Contrasting properties of B-cell and T-Contrasting properties of B-cell and T-cell linescell lines

B cellsB cells T cellsT cellsSite of maturationSite of maturation Bone marrowBone marrow ThymusThymus

Nature of surface Nature of surface markersmarkers

Immunoglobulin Immunoglobulin Several CD receptors Several CD receptors

Texture of surface Texture of surface Rough Rough Smoother Smoother

Circulation in blood Circulation in blood Low numberLow number High numbersHigh numbers

Distribution in Distribution in lymphatic organslymphatic organs

Cortex Cortex

(in follicles)(in follicles)

Paracortical (interior to the Paracortical (interior to the follicles)follicles)

Product of antigenic Product of antigenic stimulation stimulation

Plasma cells and Plasma cells and memory cellsmemory cells

Sensitized T-lymphocytes Sensitized T-lymphocytes of several types and of several types and memory cellsmemory cells

General functionsGeneral functions Production of Production of antibodies antibodies

Cell function depends on Cell function depends on type of T-lymphocytes type of T-lymphocytes subpopulationsubpopulation

Micrograph of T lymphocytes Micrograph of T lymphocytes

Light micrograph Scanning electron micrograph

Markers of maturated human Markers of maturated human T lymphocytesT lymphocytes

T-lymphocyte (subsets)T-lymphocyte (subsets) Markers (receptor) on Markers (receptor) on the cell surface the cell surface

Every T-lymphocyte Every T-lymphocyte CD2CD2 (common marker) (common marker)

T-helpersT-helpers CD4,CD4, CD3, CD28 CD3, CD28

Cytotoxic (killer) T-cellsCytotoxic (killer) T-cells CD8CD8, CD5, CD3, CD28, CD5, CD3, CD28

T-suppressorsT-suppressors CD8CD8, CD5, CD5

Delayed hypersensitivity cellsDelayed hypersensitivity cells CD4CD4

Naïve T cellNaïve T cell CD45RACD45RA

Memory T cellsMemory T cells CD45ROCD45RO, CD3, CD3

Characteristics of subsets of T cellsCharacteristics of subsets of T cells

Subset Subset Functions Functions T helper cells T helper cells ((Th, T4Th, T4))

Assist B cells in recognition of antigen; assist other Assist B cells in recognition of antigen; assist other subsets of T cells in recognition and reaction to Agsubsets of T cells in recognition and reaction to Ag

T suppressor T suppressor cells (cells (Ts, T8Ts, T8))

Regulate immune reactions; cells limit the extent of Regulate immune reactions; cells limit the extent of antibody production; block some T-cell activityantibody production; block some T-cell activity

Cytotoxic (killer) Cytotoxic (killer) cells (cells (Tc, TkTc, Tk))

Destroy a target foreign cell by lysis; important in Destroy a target foreign cell by lysis; important in destruction of complex microbes, cancer cells, virus-destruction of complex microbes, cancer cells, virus-infected cells, graft rejection; allergyinfected cells, graft rejection; allergy

Delayed Delayed hypersensitivity hypersensitivity cells (cells (Td, TdthTd, Tdth))

Responsible for allergic occurring several hours or Responsible for allergic occurring several hours or days after contact with Ag; skin reaction as in days after contact with Ag; skin reaction as in tuberculosis testtuberculosis test

Memory T cellsMemory T cells Develop from T-helpers and T-killers. Remain Develop from T-helpers and T-killers. Remain following an infection and are ready to mount a following an infection and are ready to mount a immune response more rapidlyimmune response more rapidly

Antigen presentation to helper T cell. Antigen presentation to helper T cell. Cooperation of T helper and B cellCooperation of T helper and B cell

T helper

T helper

B cell

MO

MO Antigen

macrophage

MHC II

Stages of cell-mediated cytotoxicity and the Stages of cell-mediated cytotoxicity and the action of lymphotoxins on virus-infected cellsaction of lymphotoxins on virus-infected cells

Cancer cell is attacked by Cancer cell is attacked by killer T cellskiller T cells

T lymphocytes Cancer cell

The third line of defense The third line of defense

The third line of defense is specific immune factors

(antibodies and T-lymphocytes)

Features of innate and acquired Features of innate and acquired immunityimmunity

Feature Feature Innate Innate Acquired Acquired Antigen-dependent Antigen-dependent specificity specificity

Yes Yes Yes Yes

Immunologic Immunologic memory memory

No No Yes Yes

((enhancing during enhancing during repeated contact with repeated contact with

antigenantigen))

Dependence on Dependence on В- В- andand Т- Т-lymphocytes lymphocytes

No No Yes Yes

Cell-effectors Cell-effectors Phagocytes, basophiles, Phagocytes, basophiles, eosinophils, natural killer eosinophils, natural killer cellscells,, mastocytesmastocytes

Т- і В- Т- і В- lymphocytes lymphocytes

Humoral effectors Humoral effectors Complement, cytokines, Complement, cytokines, interferons, interferons,

Antibodies Antibodies

Types of acquired immunity Types of acquired immunity

Acquired immunity

Natural Artificial

Active Passive Active Passive

Features of acquired immunityFeatures of acquired immunity

Type Type PropertiesProperties

Naturally acquire Naturally acquire activeactive

Antibodies and specialized lymphocytes acquired Antibodies and specialized lymphocytes acquired after natural exposure to a foreign agent (past after natural exposure to a foreign agent (past infectious immunity). Long lasting, specificinfectious immunity). Long lasting, specific

Naturally acquire Naturally acquire passivepassive

Transfer of antibody to agent from mother to fetus Transfer of antibody to agent from mother to fetus through the placenta (IgG) or with breast milk (IgA). through the placenta (IgG) or with breast milk (IgA). Temporary Temporary

Artificially Artificially acquired activeacquired active

Acquired following immunization, for example with Acquired following immunization, for example with poliovirus vaccine (past vaccine immunity) ; long-poliovirus vaccine (past vaccine immunity) ; long-lasting, specificlasting, specific

Artificially Artificially acquired passiveacquired passive

Acquired by administration of protective antibodies; Acquired by administration of protective antibodies; for example, the transfer of preformed antibodies, for example, the transfer of preformed antibodies, gamma globulin for hepatitis, temporary gamma globulin for hepatitis, temporary

Classification of natural immunityClassification of natural immunity

Anti-infectious Anti-infectious Anti-bacterialAnti-bacterial

Anti-viralAnti-viral

Anti-toxic Anti-toxic

Anti-fungal Anti-fungal

Anti-protozoa Anti-protozoa

Noninfectious Noninfectious Auto-immune Auto-immune

Associated with Associated with transplantation transplantation

Anti-tumoral Anti-tumoral

ReproductiveReproductive

Fundamental features of specific Fundamental features of specific immune response immune response

The response involves two sets of lymphocytes acting The response involves two sets of lymphocytes acting together with the phagocytic cells.together with the phagocytic cells.

The response is highly specificThe response is highly specific ( (a response made to one a response made to one disease generally confers immunity only to that disease and not to disease generally confers immunity only to that disease and not to

others).others). The response has memory so that once the host has The response has memory so that once the host has responded to a foreign invader, a second response to responded to a foreign invader, a second response to the same foreign invader is more rapid and greatly the same foreign invader is more rapid and greatly enhanced.enhanced.

The response is capable of discriminating between host The response is capable of discriminating between host and foreign substances.and foreign substances.

Functions of immune systemFunctions of immune system

searching

recognition

destruction

of foreign, nonself substances

Human major histocompatibility Human major histocompatibility complex (MHC)complex (MHC)

Characteristic of MHC antigensCharacteristic of MHC antigens MHCMHC – – MMajor ajor HHistocompatibility istocompatibility CComplexomplex HLAHLA – – HHuman uman LLeukocyte eukocyte AAntigen ntigen This receptor complex plays a vital role in recognition of self by the This receptor complex plays a vital role in recognition of self by the

immune system and in rejection of foreign tissue. immune system and in rejection of foreign tissue.

MHC IMHC I antigen presents on the surface of every nucleus- antigen presents on the surface of every nucleus-contained cell and is marker of self. MHC I regulates contained cell and is marker of self. MHC I regulates acceptance or rejection of tissue grafts.acceptance or rejection of tissue grafts.MHC IIMHC II antigens located primarily on macrophages and antigens located primarily on macrophages and B cells and regulate immune response. It functions in B cells and regulate immune response. It functions in cooperative immune responses to antigens mounted by cooperative immune responses to antigens mounted by these cells and T-cells. these cells and T-cells. MHC IIIMHC III genes code for certain secreted complement genes code for certain secreted complement components such as C2 and C4.components such as C2 and C4.

Antigens (Ag) Antigens (Ag)

The word The word antigenantigen is a combination of the is a combination of the words words antiantibody and body and gengenerator.erator.

AntigensAntigens are substances that are are substances that are genetically foreign and can trigger the genetically foreign and can trigger the development of specific immune reactions development of specific immune reactions after penetration in organismafter penetration in organism

Major properties of antigensMajor properties of antigens

ForeignnessForeignness (meaning that it is not a normal (meaning that it is not a normal constituent of the body)constituent of the body)

ImmunogenicityImmunogenicity ( (antigenicity) (ability to stimulate antigenicity) (ability to stimulate antibody formationantibody formation))SpecificitySpecificity

Chemical categories of antigensChemical categories of antigens

Chemicals Chemicals Object Object

Proteins and Proteins and polypeptides polypeptides

Enzymes, albumin, antibodies, hormones, Enzymes, albumin, antibodies, hormones, exotoxinsexotoxins

Lipoproteins Lipoproteins Cell membraneCell membrane

Glycoproteins Glycoproteins Viral envelope Viral envelope

Nucleoproteins Nucleoproteins (DNA complexed to proteins, but not pure (DNA complexed to proteins, but not pure DNADNA

Polysaccharides Polysaccharides Bacterial capsuleBacterial capsule

Lipopoly-Lipopoly-saccharides saccharides

Cell wall of gram-negative bacteria Cell wall of gram-negative bacteria

Antigenic determinant (epitop)Antigenic determinant (epitop)

Antigen

Epitops

Antigens determinants of virus Antigens determinants of virus

(a) Microbes such as viruses present various sites that serve as separate antigenic determinants.

(b) Inset indicates that each determinant (1, 2, 3, 4) will stimulate a different lymphocyte and antibody response.

Antigen structure of bacteriaAntigen structure of bacteria

О-antigen

(cell wall)

К-antigen

(microcapsule)

Н-antigen

(flagella)

Haptens Haptens Hapten is a small foreign molecules that consist only of a determinant group and are too small by themselves to elicit an immune response

Hapten has foreignness and specificity but has not immunogenicity

When hapten combine with larger molecule-carrier such protein it can become antigenic