Immune System Flashcards
Primary structures
Thymus and Red bone marrow
Secondary structures
Tonsils, lymph nodes, spleen, and MALT in small intestines
Maintain naïve lymphocytes and initiate an adaptive immune response
Sites of lymphocyte activation by antigens
Two partially overlapping lines of defense
Innate immunity and Adaptive (Acquired) immunity
Innate immunity
Found in nearly all forms of
life
Defense is always present
Response is non-specific
Exposure leads to immediate maximal response
Cell-mediated (neutrophil
phagocytes) and humoral
(complement proteins)
components
No immunological memory
Barriers, cells (phagocytic),
and destructive molecules
Adaptive (Acquired) immunity
Found only in jawed vertebrates (fishes, amphibians, reptiles, birds,
and mammals)
Defense must be activated
Pathogen- and antigen-specific response
Lag time between exposure and maximal response
Cell-mediated (T cells) and humoral (B cells) components
Exposure leads to immunological memory
B cells (lymphocytes) and T cells (lymphocytes)
Lymphatic vessels
A network of channels all over the body that carries lymphocytes to the lymphoid organs and bloodstream.
Transports interstitial fluid (as lymph) back to the blood circulation
Peyer patches
Very large clusters of lymphoid follicles located in the wall of the ileum which allow close monitoring of microorganisms in the gut.
Multiple sclerosis (MS)
An auto-immune and neurodegenerative disorder in which the immune system attacks the myelin of oligodendrocytes, interfering with their activity.
It is the most common autoimmune disorder
affecting the CNS.
T lymphocytes (T cells) and microglia, which phagocytose and degrade myelin debris, play major roles.
Basophils
Innate
Function: Release of histamine and other molecules involved in inflammation
Eosinophiles
Adaptive
Function: Kill antibody-coated parasites
Phagocytes
Neutrophils (I)
Mast Cells (I)
Monocytes (I, A)
Macrophages (I, A)
Dendritic cells (I, A)
Neutrophils
Innate
Function: Stimulate inflammation
Mast Cells
Innate
Function: Release histamine
Monocytes
Innate and Adaptive
Function: Develop into macrophages and dendritic cells
Macrophages
Innate and Adaptive
Function: Antigen presentation
Dendritic Cells
Innate and Adaptive
Function: Present antigens to T cells
Lymphocytes
B Lymphocytes (A) T Lymphocytes (A) Natural Killer Cells (I, A)
B Lymphocytes
Adaptive
Function: Differentiate to form antibody producing cells and memory cells
T Lymphocytes
Adaptive
Function: Kill pathogen-infected cells; regulate activities of other WBCs
Natural Killer Cells
Innate and Adaptive
Function: Attack and lyse virus-infected or cancerous body cells
Adaptive Immunity I
Triggered when the innate immune system cannot defeat the pathogen.
Adaptive immunity eliminates pathogens by two types of defense:
Humoral
Cell-mediated
Humoral
Immunity is antibody-driven and the players are plasma cells (B lymphocytes)
Cell-mediated
Immunity is cytotoxic (destroys cells), and T lymphocytes and antigen presentation are the players.
B Lymphocytes and T Lymphocytes Secretory products
B Lymphocytes: Antibodies
T Lymphocytes: Cytokines
B Lymphocytes and T Lymphocytes Site of maturation
B Lymphocytes: B lymphocytes both originate and mature in the bone marrow.
T Lymphocytes: T lymphocytes mature in the thymus after its origination in the bone marrow.
B Lymphocytes and T Lymphocytes Receptors
B Lymphocytes: B cell receptors are cell membrane antibodies (immunoglobulins) and
recognize antigens in native state
T Lymphocytes: T cell receptors differ from membrane antibodies; each T cell has a unique TCR (T cell receptor) to recognize a wide variety of antigens,
but only fragments of antigens.
B Lymphocytes and T Lymphocytes Position
B Lymphocytes: Mature B cells occur mostly outside the lymph node.
T Lymphocytes: Mature T cells occur mostly inside the lymph node.
B Lymphocytes and T Lymphocytes Types of active cells
B Lymphocytes: B cells differentiate into plasma cells and memory cells.
T Lymphocytes: T cells differentiate into many subsets of T cells such as cytotoxic T cells and helper T cells.
B Lymphocytes and T Lymphocytes Relationship
B Lymphocytes: B cells are a type of APC (antigen-
presenting cell), and present antigens to T cells.
T Lymphocytes: T cells help to activate B cells and aid in antibody production against antigens.
Antigens
Free molecules (e.g., proteins or polysaccharides) or molecules that are parts of intact cells (bacteria, protozoa, or tumor cells).
Epitopes or antigenic
determinants
Immune system cells recognize and react to these small molecular regions of the antigen
How are the different antigens recognized? What is the nature
of the immune response?
Humoral: B lymphocytes, as part of their B cell receptors, produce
antibodies that bind the antigen.
Cellular: T lymphocytes have T cell receptors in the cell membrane, which bind to the antigen to later eliminate it in different ways.
Antibodies
A glycoprotein of the immunoglobulin family that
interacts specifically with an epitope (antigenic determinant).
secreted by plasma cells, which arise from B lymphocytes.
Antibody variable regions (Fab)
The site to which the antigen binds.
The genes are re-arranged (recombination) to “match” an antigen after B lymphocytes are activated against a specific antigen. This recombination produces a huge number of possible antibodies
Antibody constant region (Fc)
Binds to surface receptors on the cells.
How Antibodies Work
Specific binding of antigens by an antibody can:
• Neutralize antigens
• Precipitate antigens
• Agglutinate (clump) microorganisms bearing the
antigens.
Fc portions of antibodies attached to cell-surface antigens bind to complement proteins
and surface receptors on many WBCs.
Hypersensitivity
An adaptive immune response that damages the body’s own tissues.
Type I hypersensitivity
an immediate or anaphylactic reaction, often associated with allergy.
Antigen presentation
A vital immune process that triggers T cells into action.
Phagocytic cell engulfs a cell infected with virus or a
bacterium, break down the proteins
Then “presents” the antigen fragments bound to MHC (Major histocompatibility complex) proteins at the cell surface.
Antigens recognized by a receptor on T cell and trigger immune responses of T cells
Humoral antigen presentation in adaptive immunity responses
Immunity is antibody-driven and the players are plasma cells (B lymphocytes).
Antigen presentation triggers naïve T helper cells to activate B cells that become plasma cells. These release antibodies.
Cell-mediated antigen presentation in adaptive immunity responses
Immunity is cytotoxic (destroys cells), and T lymphocytes are the players.
Antigen presentation activates naïve cytotoxic T cells, which then bind and kill all cells with that antigen exposed.
Cytokines
Small polypeptide or glycoprotein molecules
secreted by T lymphocytes.
Involved in both innate and adaptive immunity.
During inflammation or tissue injury, immune cells
communicate with each other via cytokines to coordinate defenses.
Cytokines coordinate cell activities in both innate and adaptive immune responses in several ways:
Directed cell movements, or chemotaxis, and cell accumulation at sites
of inflammation.
Increasing mitotic activity in leukocytes.
Stimulation or suppression of lymphocyte activities in adaptive immunity.
Stimulation of phagocytosis by innate immune cells.
Acquired immunodeficiency syndrome (AIDS)
The retrovirus that produces acquired immunodeficiency syndrome (AIDS) infects and rapidly kills helper T cells.
Reduction of this key lymphocyte group
cripples the patient’s immune system rendering them susceptible to bacterial, fungal, protozoan, and other infections
Red Bone Marrow
A key component of the lymphatic system, producing the lymphocytes that support the body’s immune system. About 16% of its cells are lymphocytes.
Responsible for both the creation of T cells and
the production and maturation of B cells.
Cortex of the Thymus
The cortical zone of an
active thymus is packed with small, highly basophilic T lymphoblasts (thymocytes)
that proliferate.
Functions of the Thymus
T cells actually arrive at the thymus (from the bone marrow) as T lymphoblasts (= thymocytes), meaning they have not yet differentiated.
T cells become either naïve helper T cells or naïve cytotoxic T cells
lymphoid nodules or follicles
Large aggregates of B lymphocytes called lymphoid nodules or follicles transiently
characterize all secondary lymphoid organs.
Lymph Node
The three major regions of a lymph node include the outer cortex receiving lymph from the afferent lymphatics, an inner
paracortex, and a central
medulla with sinuses converging at the efferent lymphatic.
Filters lymph and facilitates in antibody production.
Mucosa-Associated Lymphoid Tissue (MALT)
Consists of diffuse lymphoid tissue, composed of lymphoid nodules in the mucosa of the digestive, respiratory, and urogenital systems.
- Tonsils
- Peyer patches
- Appendix
Tonsils
Masses of lymphoid nodules comprising tonsils are collected in three
general locations in the wall of the pharynx.
Palatine tonsils are located in the posterior lateral walls of the oral cavity.
Lingual tonsils are along the surface of the posterior third of the tongue.
The pharyngeal tonsil is a single medial mass situated in the posterior wall of the nasopharynx.
Appendix
A blind evagination off the cecum, the appendix is a significant part of the MALT; its lamina propria and submucosa are filled with lymphocytes and lymphoid follicles
