CHAPTER 3: Adaptive Immunity (specific body defense system)
Immunity: refers to the ability of an organism to recognize and defend itself against infectious agents
Susceptibility: opposite of immunity, is the vulnerability of the host to harm by infectious agents
Immunology: the study of adaptive immunity and how the immune system responds to specific infectious agents and toxins
Immune system: consists of various cells, especially lymphocytes, and organs such as the thymus gland, that help provide the host with specific immunity to infectious agents
Innate immunity (genetic): exists because of genetically determined characteristics
All humans have immunity to many infectious agents that cause disease in pets and domestic animals
Adaptive immunity (acquired): immunity obtained in some manner other than heredity
Naturally acquired adaptive immunity is most often obtained by having a specific disease
Artificially acquired adaptive immunity is obtained by receiving an antigen by injection of vaccine or immune serum
Formed cellular elements of the blood
The Bursa of Fabricus
In chickens this is where B cells develop
B-lymphocyte- B cellHumoral immunity (antibodies)
T-Lymphocyte-T cellInvolved cell mediated
All distributed to the entire body by,Peyers path and nodule in digestive trace,Spleen, lymph nodes , blood and thymus
Lymphocytes give rise to two major types of immune responses
1. Humoral immunity: carried out by antibodies circulating in the blood
2. Cell mediated immunity: carried out by T cells and occurs at the cellular level
Specific immune responses are carried out by lymphocytes which develop from stem cells as do other white blood cells, red blood cells, and platelets
B lymphocytes (B cells): lymphocytes are processed and mature in tissue, referred to as bursal-equivalent tissue
T lymphocytes ( T cells): stem cells migrate to the thymus, where they undergo differentiation into thymus-derived cells
Definition-A network of conduits(vessels) carry a clear fluid called lymph.Travel only one way flow towards the heart.
The lymphatic system can be broadly divided into the conducting system and the lymphoid tissue.
The conducting system carries the lymph and consists of tubular vessels that include the lymph capillaries, the lymph vessels, and the right and left thoracic ducts.
The lymphoid tissue is primarily involved in immune responses and consists of lymphocytes and other white blood cells
Regions of the lymphoid tissue densely packed with lymphocytes are known as lymphoid follicles.
Lymphoid tissue- either structurally well organized as lymph nodes or loosely organized lymphoid follicles known as the mucosa-associated lymphoid tissue (MALT)
Lymp (contain plasma cell and excess fluid between spaces cell)
Flow in lymph capillaries->lymph vessel->passes through lymph nodes->return to venous blood
by lymphatic duct (right or left) Movement of lymph is by mechanical contraction of
skeleton muscle.
tonsil
Thymus gland
spleen
Lymph nodes
Lymphatic vessel
•it is responsible for the removal of interstitial fluid from tissues
•it absorbs and transports fatty acids and fats as chyle to the circulatory system
•it transports immune cells to and from the lymph nodes in to the bone
•The lymph transports antigen-presenting cells (APCs), such as dendritic cells, to the lymph nodes where an immune response is stimulated.
•The lymph also carries lymphocytes from the efferent lymphatics exiting the lymph nodes
FUNCTION OF LYMPHATIC SYSTEM
Including , primary lymphoid organ-thymus and bone marrow Function- production and selection of lymphocytes Secondary lymphoid organ- lymph nodes, and the
lymphoid follicles in tonsils, Peyer's patches, spleen, adenoids, skin
Function - maintain mature naive lymphocytes and initiate an adaptive immune response
environment for the foreign or altered native molecules (antigens) to interact with the lymphocytes
Y-shaped protein molecules composed of four polypeptide chains – two identical light (L) chains and two identical heavy (H) chains
Constant regions: determines the particular class that an immunoglobulin belongs to
Variable regions: each chain have a particular shape and charge that enable the molecule to bind a particular antigen
Five classes of immunoglobulins have been identified in humans and other higher vertebrates
1. IgG: the main class of antibodies found in the blood accounts for as much as 20% of all plasma proteins
2. IgA: occurs in small amounts in blood and in larger amounts in body secretions (tears, milk, saliva and mucus)
3. IgM: found as a monomer on the surface of B cells and is secreted as a pentamer by plasma cells
4. IgE: has a special affinity for receptors on the plasma membranes of basophils in blood or mast cells in tissues
5. IgD: found mainly on B-cell membranes and is rarely secreted
The Structures of the Different Classes of Antibodies
IgA
IgM
IgE
IgG
IgD
In humoral immunity the primary response to an antigen occurs when the antigen is first recognized by host B cells
Primary response of B cells can occur by two mechanisms:1. B cells can be activated by binding antigen, proliferating
and forming plasma cells (T-independent antigens)2. Produces IgM antibody and no B memory cells are formed
(T-dependent antigens) Secondary response: when an antigen recognized by
memory cells enters the blood
Primary and Secondary Responses to an Antigen
Produces IgM antibody and no B memory cells are formed (T-dependent antigens)
Primary and Secondary Responses to an Antigen
Antibodies produced by humoral immune responses eliminate foreign agents in three ways:
1. Neutralization
2. Opsonization
3. Immune complexes
Summary of Humoral Immunity
Involves the direct actions of T cells
T cells interact directly with other cells that display foreign antigens
Involves the differentiation and actions of different types of t cells and production of chemical mediators (cytokines)
Cytokines: lymphokines and interleukins
Types of T cells: After T cells are challenged by antigens, the cells differentiate into one of several types of functioning T cells
Involves the response of T lymphocytes
T cells cannot be activated directly by antigens
Macrophages that have processed an antigen secrete the lymphokine interleukin-1 (IL-1), which activates T helper cells
T helper cells secrete interleukin-2 (IL-2) and activate delayed hypersensitivity cells and cytotoxic killer cells
IL-1 and IL-2 cause undifferentiated cells to become natural killer cells
The Reactions in Cell-Mediated Immunity
Summary of Cell-mediated Immunity: “CD” stands for cluster of differentiation