ADAPTIVE IMMUNITY Flashcards
ADAPTIVE IMMUNITY
• Characteristics:
• Specificity for individual pathogens
• Ability to remember prior exposures
• Increased response upon repeated exposure
Adaptive immunity involves
Lymphocytes
T cells/lymphocytes
Mature in the thymus
Regulatory role
Help B cells respond to antigens
Kill virally infected target cells
Mature in the bone marrow
Differentiate into plasma cells
Produce antibodies
B cells/lymphocytes
ADAPTIVE IMMUNITY
Based on clonal selection, expansion, and differentiation of antigen-specific T and B cells
Immunologic Memory
Results of Immunologic Memory
Greater speed and intensity in response to re-encounter with the same pathogen
Protects host from reinfection
ADAPTIVE IMMUNITY
Lymphocyte Maturation
• Differentiation starts very early in…..
• Develops specificity and destroys possible…
• Involves well-orchestrated signaling
mechanisms
fetal development
self-reactive cells
Lymphocyte maturation
• Outcomes:
Creation of a wide variety of antigen-
specific receptors
Selection of helpful cells while avoiding
harmful ones
T-CELL DIFFERENTIATION
- Differentiation occurs in the thymus
• T Cells (60-80%)
Thymus
Outer cortex and inner medulla
• Early precursors enter the thymus at the_______ and migrate to the_____
cortico-medullary junction
outer cortex.
Chemokines
Drive migration
Recruit specific cells to particular sites
T-CELL DIFFERENTIATION
• Precursors committed to becoming T cells
• Undergo gene rearrangement for antigen receptor
• Display distinct surface markers during development
Thymocytes
T-CELL DIFFERENTIATION
• Thymocytes
• Precursors committed to becoming T cells
• Undergo gene rearrangement for antigen receptor
• Display distinct surface markers during development
Double-Negative (DN) Thymocytes
• Lack CD4 and CD8 markers
Gene Rearrangement
• Random gene rearrangement builds diversity
• TCR consists of…
• T-Cell Receptor (TCR)
alpha (a) and beta (B)
chains
DOUBLE-POSITIVE (DP) STAGE
Express both CD4 and CD8 antigens
Positive Selection
• Allows only DP cells with functional TCR receptors to survive
• T cells must recognize foreign antigen with MHC molecules
• MHC Restriction
• Selection of thymocytes interacting with host MHC antigens
DOUBLE-POSITIVE (DP) STAGE
• Negative Selection
Occurs in corticomedullary region and medulla
Eliminates clones capable of autoimmune response
Only 1-3% of DP thymocytes in the cortex survive
MATURE T CELLS
• CD4 and CD8 Markers
• CD4 and CD8 Markers
Survivors exhibit only____ marker
one
Wither 4 or 8
• CD4+ T cells recognize antigen with______
Expressed by 2/3 of peripheral T cells
Thelper cells
class II MHC
CD8+ T cells interact with antigen and class______
Expressed by 1/3 of peripheral T cells
Cytotoxic T cells
I MHC
T HELPER CELLS
• Th1 cells produce IFN-v, IL-2, and TNF-
• protect cells against _______by activating cytotoxic lymphocytes and macrophages
intracellular pathogens
T HELPER CELLS
• Th2 cells produce IL-4, IL-5, IL-6, IL-9, IL-10, and IL-13
• help B cells produce antibodies against ______and to generally regulate
B-cell activity
extracellular pathogens
T HELPER CELLS
Possess CD4 and CD25
5% of all CD4+ T cells
Suppress immune response to self-antigens
T Regulatory (Treg) Cells
T HELPER CELLS
T Regulatory (Treg) Cells
Possess______
_____of all CD4+ T cells
Suppress immune response to self-antigens
CD4 and CD25
5%
______produce_____
Have proinflammatory effect
Stimulate growth of hematopoietic cells (mast cells); may promote autoimmune inflammation
Th9 cells
IL-9
•_____ cells produce_____ and _____
.
Increase inflammation and joint destruction
Associated with autoimmune disease
Th17
IL-17 and IL-22
activated by antigens in lymph nodes or spleen
CYTOTOXIC T CELLS (Tc)
• CD8+ T cells
• Leave secondary lymphoid tissues, target infection sites
• Bind and kill infected cells via apoptosis, antigen-specific
• Recognize antigens with class I MHC complexes
• Defense against intracellular pathogens, altered host cells (tumor cells)
CYTOTOXIC T CELLS (Tc)
• CD8+ T cells
CYTOTOXIC T CELLS (Tc)
Mechanisms of Action:
Differentiate into_____, proliferate, migrate to affected tissues
Kill target cells via:
Releasing_____ (granzymes, perforins)
Inducing_____ via intracellular signaling
cytotoxic lymphocytes
granules
apoptosis
Granule-Mediated Killing:
Granules contain:
_________form pores in target cell membrane
________enter through pores, initiate cascade fragmenting target cell DNA, disrupting mitochondria
Perforins (pore-forming proteins)
Granzymes (serine proteases)
activate nuclease, destroying target cell and viral DNA
Granzymes
B CELL DEVELOPMENT
• Origin and Initial Development:
• B cells originate from _____in the_____.
• Mature entirely within the____
hematopoietic stem cells; bone marrow
bone marrow
B cell development
• The process includes three main phases:
Development of mature immunocompetent B cells
Activation by antigen
Differentiation into plasma cells for antibody production
The earliest stage requiring direct contact with stromal cells and involving several transcription factors.
Pro-B Cells (progenitor B cells):
B cells
Gene Rearrangement:
Heavy and light chain genes rearrange create specific antibody molecules.
Heavy chains:
Light chains:
Pro-B cell receptor____ interacts with stromal cell factors to trigger gene rearrangement.
chromosome 14
chromosome 2 and 22
C-Kit
PRE-B CELLS
Heavy Chain Synthesis:
• Successful rearrangement of heavy chain genes leads to the synthesis of______ and the formation of the____
u chains (IgM class)
pre-B cell receptor (pre-BCR)
PRE-B CRLLS
• Surrogate Light Chains:
u chains pair with surrogate light chains and signaling molecules
Ig-a, Ig-B
PRE-B CELL
Clonal Expansion:
• Successful pre-BCR signaling triggers clonal expansion.
Failure leads to_____.
apoptosis
IMMATURE B CELLS
• IgM Expression:
• Immature B cells express complete_____ molecules on their surface, indicating successful light chain rearrangement.
IgM
IMMATURE B CELLS
Central Tolerance:
Self-reactive B cells are eliminated via apoptosis, a process known as…
Surviving immature B cells move to the spleen to mature.
central tolerance
MATURE B CELLS
Further Differentiation:
In the spleen, B cells become_____ or_____
______remain in the spleen; follicular B cells circulate in secondary lymphoid organs
marginal zone B cells; follicular B cells
Marginal zone B cells
Express IgD along with IgM, enhancing antigen recognition
MATURE B CELLS
Lifespan and Activation:
Short lifespan unless activated by antigen
Activation transforms them into blast cells, then memory cells, and plasma cells
MATURE B CELLS
are large, with abundant cytoplasmic immunoglobulin
and an eccentric nucleus.
PLASMA CELLS
PLASMA CELLS
• Function:
Their primary role is antibody production.
They reside in peripheral lymphoid organs and the bone marrow.
T CELLS
Develop in the____
Found in blood (____of circulating lymphocytes), thoracic duct fluid, lymph nodes
Identified by_____ formation with SRBCs
End products of activation are____
Antigens include_______
Located in____ region of lymph nodes
thymus
60-80%
rosette
cytokines
CD2, CD3, CD4, CD8
paracortical
B CELLS
Develop in the_____
Found in_________
Identified by_____
End product of activation is___
Antigens include________
Located in_____ region of lymph nodes
bone marrow
bone marrow, spleen, lymph nodes
surface immunoglobulin
antibody
CD19, CD20, CD21, CD40, class II MHC
cortical
Monocyte vs Neutrophils
Neutrophils for acute infections
Monocytes for chronic infections
What determines the age of Neutrophils
of lobes
% of Neutrophils
50-70%
Chemical messengers that cause cells to migrate in a particular direction
Chemotaxis
Marginal pool
In the walls of blood vessels
Allows neutrophils to move from circulating blood to the tissues
Lifespan of neutrophils in tissue
5 days
Frustrated phagocytes
Eosinophils
Eosinophils are what %
1-3%
Capable of phagocytosis but are much less efficient than NEU because of the smaller numbers present
Eosinophils
Relationship of EO and BASO
Eosinophil is responsible for moderating Basophils’ histamine production
It releases antihistamine
During an allergic reaction the first cell to react is the
Basophils
Largest cells in peripheral blood
Monocytes
How is macrophage involved in adaptive immunity
It present antigens to T and B cells. These cells will study the anatomy of the bacteria so that on the next exposure, the IS can readily fight
Basophils vs Mast cells
Both came from the bone marrow but Basophils stays in the blood vessels whereas Mast cells are segregated in the skin
No basophils in tissue
Sometimes, mast cells can be seen in blood (rare)
More potent during allergic reaction? Why?
Mast cells
Bigger and contains more histamines. First responders during infections
Most potent allergic cell
Most potent phagocytic cell
Mast cell
Dendritic cell
Macrophages can only eat
Bacteria
MHC
Major Histocompatibility complex
Cytotoxic action
Produce perofrins and granzymes
Unsa gina indicate if may antibody naka dikit sa cell
Most likely the cell is infected. Nk cell will attach to the Fc region (Fab attaches to the antigen)
Thymosin
promotes the maturation of T-cells (a type of white blood cell) within the thymus. T-cells are essential for adaptive immunity, which is the body’s ability to recognize and remember specific pathogens.
Positive vs Negative Selection
Positive Selection: Thymocytes that can moderately bind to self-major histocompatibility complex (MHC) molecules survive. This ensures that the T-cells can recognize antigens presented by MHC molecules.
Negative Selection: Thymocytes that bind too strongly to self-antigens are eliminated to prevent autoimmunity. This process ensures that the mature T-cells are self-tolerant.
Class I MHC found in
All nucleated cells
Class II MHC found in
Antigen presenting cells (ability to phagocytose)
Th1 cells protect cells against
Th2 cells protect cells against
Intracellular pathogens
Extracellular pathogens
Potent for tumor
Cytotoxic Tcells
