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