Lecture 2: Cells and Tissues of the Adaptive Immune System Flashcards
Two major types of lymphocyes
B cells
T cells
What is critical for development of specific immunity
Interactions between T-cells and B-cells, and between T-cells and APCs
T cells develop and mature where
Thymus
What gives rise to cellular immunity
When a mature T-cell is Ag stimulated, it gives rise to cellular immunity
B-cells develop and mature where, and give rise to what
Develop and mature in the bone marrow and give rise to humoral immunity
Humoral adaptive immunity mediated by
Abs in the blood produced by B cells
What is the principal defense mechanism against extracellular microbes and their toxins?
Humoral adaptive immunity
Cellular immunity is controlled by
Responses of T-cells which function in concert with Ag-presenting cells and phagocytes
Cellular mediated immunity defends against
Intracellular microbes, such as viruses and some bacteria, which are inaccessible to circulating Abs
Function of CMI
Killing of infected host cells cell eliminate reservoirs of infecion
Helper T cells help how
Help B-cells to make effective Abs
Humoral immunity overview
B lymphocytes secrete Abs that prevent infection and eliminate extracellular microbes
CMI overview
Helper T cells activate macrophages to kill phagocytized microbes, or activate cytotoxic T cells to directly destroy infected cell
What cell responds to a macrophage with phagocytosed microbes
Helper T lymphocytes
What cell responds to a cell with intracellular microbes (e.g. a virus)
Cytotoxic T lymphocytes
What responds to extracellular microbes
B lymphocytes
Clonal expansion
Increases the number of Ag-specific lymphocytes to keep pace with microbes
Ag-specific clones of lymphocytes develop before and independent of exposure to Ag
Clonal expansion lymphocyte-Ag interaction
When Ag is introduced in individual, lymphocytes with receptors for that Ag bind it and are triggered to proliferate and differentiate into clones of cells specific for that Ag
Memory cells vs Naive lymphocytes
Memory cells are more numerous and respond faster and more effectively- generation of memory responses is an important goal of vaccination
Active immunity specificity and/or memory?
Yes to both
Passive immunity specificity and/or memory?
Yes specificity, no memory
Passive immunity
Adoptive transfer of antibodies or t lymphocytes specific for microbe
What generates immunologic memory
Only active immune responses
B-lymphocytes
Recognize soluble Ags and develop into Ab-secreting cells
T helper lymphocytes
Recognizes Ags on the surfaces of Ag-presenting cells and secrete cytokines, which stimulate mechanisms of immunity and inflammation (activate macrophages, t/b lymphocytes, inflammation)
Cytotoxic T lymphocytes
Recognize Ags on infected cells and kill them
Regulatory T cells
Suppress and prevent immune respones (e.g., to self antigens)
Primary lymph organs
Thymus and Bone marrow
Secondary lymph organs
Spleen, lymph nodes, mucosa associated lymphoid tissue
Ag-specific receptors located
On surface of T and B cells. They are the same on a single cell but vary from cell to cell
Most T-cells produced when and why
Early in life because thymus is large and then becomes smaller and replaced by fat and CT later
What plays important role in T cell developement
Cytokines
T-cells make contact with epithelial cells, DCs, and macrophages where
In the thymus
Generation of naive lymphocytes
Pluripotent stem cells in bone marrow migrate to thymus to develop
Helper T cells express what and provide
CD4 and provide help for B-cell growth/differentiation
Cytotoxic T cells express and do what
CD8 and recognized and kill virus infected cells
Functionally mature T cells migrate where
To secondary lymphoid tissues to mediate protection
Bone marrow produces
WBCs, RBCs, and platelets
Bone marrow color at ages
Birth- all red
Puberty-starts converting to yellow
Adults- half red half yellow
Differentiation of B cells occurs where in fetus and adult
Fetus- liver
Adult- bone marrow
Development of B cells involves contact with
Stromal cells and cytokines
Lifetime production site of B cells is
Bone marrow
Where are lymphocytes NOT found
Eye, Brain, Testicles
Lymphocytes enter secondary lymph organs through
High endothelial venules HEVs
Diapedesis
Method by which lymphocytes migrate from blood into the tissue in response to cytokines
How do lymphocytes re-enter the circulation
Efferent lymph vessels
Activation of B cells
Naive B cells migrate to secondary lymph tissues where they look for and respond to soluble foreign Ags
Activated B cells do what
Proliferate and mature into memory cells or plasma cells
Plasma cells are
Terminally differentiated B cell which produce and secrete Abs
Spleen white pulp
Made up of T cell and B cells
Periarteriolar lymphoid sheath composed of
T cells
Lymphoid follicle composed of
B cells
T-cell activation
Naive T cells travel to secondary lymph organs and are activated by Ags
Then differentiate into effector or memory T cells
Some effector/memory t cells migrate back into peripheral sites of infection
Some stay in the lymph nodes and help Ag-activated B cells to become “an Ab factory”
Dendritic cells enter the lymph node through what and migrate where
Afferent lymphatic vessels and migrate to T cell rich areas
Another name for secondary lymph follicle
Germinal center- occurs after Ag stimulation
Professional Antigen presenting cells (APCs) include
Dendritic cells
Tissue macrophages
B cells
T or false- B cells require and APC
False, T cells require APCs
What activates naive T cells in the Lymph nodes
Only dendritic cells can do this
Macrophages and B cells can present Ags to
Activated T cells but not naive T cells
Cellular link b/w innate and adaptive immunity
DCs and macrophages are innate cells and therefor provide a link between the two immunity types
DCs are from what lineage
Myeloid lineage
myeloid DCs are derived from
Monocytes
Classical DCs, pDCs and Langerhans cells develop from
Directly from stem cells
How do DCs aquire Ags
Receptor mediate endocytosis/pinocytosis
Activated DCs secrete
Cytokines
Classical DCs reside where and migrate where
Skin, mucosa, organ parenchyma.
Migrate to LNs where they display Ags to T cells
Plasmacytoid DCs (pDCs) function
Early cellular responders to viral infection
Recognize nucleic acid of intracellular viruses and produce soluble interferons (IFN-a/b)
