The Immune System

Antigens and antibodies

Major functions of the Lymphatic & Immune systems

Anatomy of the lymphatic system

Humoral response and cellular response

immune defenses

Cells involved in the immune system

Disorders associated with the Immune system

Adaptive(acquired)

Innate (natural)

First line of defense: external body membranes

Second line of defense: antimicrobial proteins, phagocytes, and other cells.

Third line of defense attacks particular foreign substances

Similarities

Both release and recognize many of the same defensive molecules

Have specific pathways for certain substances

Release proteins that alert cells of adaptive system to foreign
molecules

Humoral immunity B cells Cellular immunity T cells

monocytes/macrophages

Develop from monocytes and are chief phagocytic cells; most robust phagocytic cell.

Phagocytes

white blood cells that ingest and digest (eat) foreign invaders

Neutrophils are the most abundant phagocytes, but die fighting; become phagocytic on exposure to infectious material.

NK cells

Kill by inducing apoptosis in cancer cells and virus-infected cells

Attack cells that lack “self” cell-surface receptors

Secrete potent chemicals that enhance inflammatory response

Cellular

T cells

Some T cells directly kill cells; others release chemicals that regulate immune response

T cells are more complex than B cells both in classification and function

Two populations of T cells

CD8 cells

CD4 cells

y become helper T cells (TH) that can activate B cells, other T
cells, and macrophages; direct adaptive immune response

Some become regulatory T cells, which moderate immune response

become cytotoxic T cells

Also become memory T cells

Pus

creamy yellow mixture of dead neutrophils, tissue/cells, and living/dead pathogens

Some bacteria, such as tuberculosis bacilli, resist digestion by macrophages and remain
alive inside

Can form tumorlike growths called granulomas—area of infected macrophages surrounded by uninfected macrophages and outer capsule

Phagocytize pathogens that enter tissues, then enter lymphatics to present
antigens to T cells in lymph node

Primary Lymphoid organs

Secondary Lymphoid organs

Thymus

Red Bone Marrow

Spleen

Peyers Patches

Tonsils

Appendix

Lymph Nodes

Site for lymphocyte activation and proliferation

Cleanse Lymph

stop germs entering the body through the mouth or the nose.

contain a lot of white blood cells

lymphoid tissue aggregates situated near the entrance of the digestive and respiratory tracts

Cleanses blood and removes aged or defective red blood cells

Stores platelets, monocytes, and proliferation

SIte for lymphocyte activation and proliferation

lymphoid follicles in the mucus membrane that lines your small intestine

similar to lymph nodes

function as a lymphoid organ, assisting with the maturation of B lymphocytes and in the production of the class of antibodies known as immunoglobulin A (IgA) antibodies

Acquired immune deficiency syndrome (AIDS)/Human immunodeficiency virus (HIV)

Cripples immune system by interfering
with activity of helper T cells

HIV destroys TH cells, thereby depressing cellular immunity

HIV is transmitted via body fluids: blood, semen, and vaginal secretions

Severe combined immunodeficiency (SCID) syndrome

genetic defect with marked deficit in B and T cells

Hodgkin’s disease

Autoimmune disease

acquired immunodeficiency that causes cancer of B cells,
which depresses lymph node cells and thus leads to immunodeficiency

results when immune system loses ability to distinguish self from
foreign

Autoimmunity

production of autoantibodies and sensitized TC cells that destroys body tissues

Examples

– Rheumatoid arthritis: destroys joints

– Myasthenia gravis: impairs nerve-muscle connections

– Multiple sclerosis: destroys white matter myelin

T cells provide defense against intracellular antigens

Humoral

Active humoral immunity :

Passive humoral immunity

occurs when B cells encounter antigens and produce
specific antibodies against them

Artificially acquired

Naturally acquired

occurs when ready-made antibodies are introduced into
body

Artificially acquired

Naturally acquired:

B cells are not challenged by antigens; Immunological memory does not occur

Antibodies

Antigens

Basic antibody structure

Two identical heavy (H) chains with hinge region at “middles”
Two identical light (L) chains

Overall T- or Y-shaped antibody monomer consists of four looping polypeptide
chains linked by disulfide bonds

Five major classes: IgM, IgA, IgD, IgG, and IgE

Antibody targets and functions

Form antigen-antibody (immune) complexes

Defensive mechanisms used by antibodies

Neutralization, Agglutination, Precipitation, Complement fixation

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Neutralization, Agglutination, Precipitation, Complement fixation and activation

substances that can mobilize adaptive defenses and provoke an immune response

Targets of all adaptive immune responses

Most are large, complex molecules not normally found in body (nonself)

Characteristics of antigens

Can be a complete antigen or hapten (incomplete)

Contain antigentic determinants

Can be a self-antigen

2nd line of defense (cells and chemicals)

1st line of defense (surface barriers)

skin and mucous membranes, along with their secretions

Skin and mucous membranes produce protective chemicals that inhibit or destroy microorganisms

Enzymes

Mucin

Acid

Respiratory system also has modifications to stop pathogens

Surface barriers breached by nicks or cuts trigger the internal second line of defense that protects deeper tissues

Innate system necessary if microorganisms invade deeper tissues

  • Phagocytes
    – Natural killer (NK) cells