BIOL 100 Chapter Notes - Chapter 41: Adaptive Immune System, Natural Killer Cell, Innate Immune System
Textbook Notes
Chapter 41
Adaptive Immune System
Concept 1: Blood and the Immune System
Adaptive Immunity
More specialized and it supplements the protection provided by innate immunity
Present only invertebrates
Ability to recognize specific pathogens
While the innate immune system may recognize bacteria in general, the adaptive immune system will
recognize a specific bacterium
Blood and the Immune System
The peripheral blood contains 20–50% of circulating lymphocytes; the rest move in the lymph system
Roughly 80% of them are T cells, 15% B cells and the remainder are undifferentiated cells
Lymphocytes constitute 20–40% of the body's white blood cells
Main Cells Involved inAdaptive Immunity: B and T cells
B and T cells which are initially derived from bone marrow
Hematopoiesis - form through this process which refers to the process of making the cells found in blood
Bone marrow-derived stem cells differentiate into either mature cells of the immune system or
into precursors of cells that migrate out of the bone marrow to continue their maturation elsewhere
Bone Marrow
Produces B cells, natural killer cells, granulocytes, and immature thymocytes in addition to red blood cells and
platelets
B cells - responsible for the humoral response to infection, which includes the production of antibodies that will
interact with the bacteria displaying antigen, or foreign protein on their surfaces
Humoral response - antibodies, which are secreted and enter the blood stream
Production of 'memory' of the invading pathogen and are termed Memory B cells
T cells - immature thymocytes leave the bone marrow and migrate into the thymus
Function of the thymus
Responsible for the cell mediated response to infection
T-Cells Producing
Lymphatic organs - lymphocyte maturation, differentiation, and proliferation take place
Primary lymphoid organs (bone marrow and thymus)
Bone marrow is the ultimate source of all blood cells including immune cells
The primary lymphoid organs are those in which the maturation of T and B lymphocytes into
antigen-recognizing cells takes place
Secondary lymphoid tissue
Mature B and T lymphocytes migrate from the primary lymphoid organs through the
bloodstream to the secondary lymphoid organs
Organs in which antigen-committed lymphocytes are stimulated by antigens to undergo further
division and differentiation
Lymphatic system - filters the blood for foreign proteins
Originates at the capillary level and is carried to the lymph nodes where it is filtered
Lymph is ultimately recycled back into the blood through the subclavian veins in the right side of the
heart
Lymph Nodes
Home of both the B and T cells
Following features:
Afferent channels which transfers the lymph from the capillaries to the lymph node
Lymph first encounters dendritic cells and macrophages which are involved in the innate immune
response
Lymph then enters the outer cortex where it encounters the B cells
Lymph then enters the lymph sinuses and deep cortex where it encounters the T cells
Lymph then enters the medullary sinuses which have B cells and plasma cells
Lymph then leaves the lymph node by way of the efferent duct and ultimately travels to the venous side
of the heart
Adaptive Immune Response
Occurs mainly in the secondary lymphoid organs
Pathogens and their secreted antigens are trapped in these secondary lymphoid tissues, and presented to naive
lymphocytes that are passing through
Microorganisms that enter the body through the skin or the lungs drain to the regional lymph nodes where they
stimulate an immune response
Concept 2: T-Cells
Major Histocompatibility Complex (MHC)
Peptides - healthy cells produce small fragments of protein which are displayed on the surface of the cell
T-cells recognize these peptides as 'friendly'
If the cell is infected and is making foreign protein, it will display some of the foreign protein on the
surface of the cell and signal to the T cells that this is an 'unfriendly' cell and it should be killed
The normal peptides and the foreign peptides are displayed on this host protein
Histocompatilibty - signified if the cell is friendly or compatible
Antigen - peptide that is expressed on the MHC and it can either be 'self' or 'non-self' or friendly and not
friendly
This process prevents the T cells from killing healthy host cells, but allows for the killing of infected or
abnormal cells
MHC molecules - play a crucial role in the response of T cells to antigens that penetrate or are endogenous inside
the cells of the body
Codes for two major categories of cell surface transmembrane molecules, MHC class I and MHC class II
molecules
MHC class I - expressed on all nucleated cells
Document Summary
More specialized and it supplements the protection provided by innate immunity. While the innate immune system may recognize bacteria in general, the adaptive immune system will recognize a specific bacterium. The peripheral blood contains 20 50% of circulating lymphocytes; the rest move in the lymph system. Roughly 80% of them are t cells, 15% b cells and the remainder are undifferentiated cells. Lymphocytes constitute 20 40% of the body"s white blood cells. Main cells involved inadaptive immunity: b and t cells. B and t cells which are initially derived from bone marrow. Hematopoiesis - form through this process which refers to the process of making the cells found in blood. Bone marrow-derived stem cells differentiate into either mature cells of the immune system or into precursors of cells that migrate out of the bone marrow to continue their maturation elsewhere. Produces b cells, natural killer cells, granulocytes, and immature thymocytes in addition to red blood cells and platelets.
