Anatomic and cellular basis of immune response Flashcards
Organization of Immune system
What 2 overlapping compartments
• Lymphoid system
Central and Peripheral
• Reticuloendothelial system
Circulating monocytes
Resident macrophages
Macrophage like cells –
dendritic cells (lymp nodes),
glial cells (nerve)
Langerhan’s cells (skin)
Functions of immune system
Lymphoid organs
- protection against foreign agents
- orchestrate functions of immune system – cytokines (lymphokines)
RES
- phagocytosis & intracellular killing
- recruiting inflammatory cells by cytokine (monokines) - antigen presenting to lymphocytes to initiate antigen-
specific immunity
Structural organs/tissues
Two groups of lymphoid organs
• Primary - thymus and bone marrow
• Secondary - lymph nodes, spleen, mucosal & submucosal tissues of alimentary & respiratory tracts
Types of lymphocytes
• T and B cells - responsible for antigen-specific immunity
T cells – Cell mediated immunity
B cells – Humoral immunity - antibody formation
• NK cells - cytotoxic to tumor cells & cells expressing foreign antigens
Development: Pluripotent Bone Marrow Stem Cells
Immune System cells are derived from pluripotent hematopoietic stem cells in the bone marrow.
bone marrow➡️ pluripotent stem cell➡️ lymphoid progenitor cell ➡️ B cell precursor ➡️ Mature B cell
Leukocytes
White blood cells that provide either innate or specific adaptive immunity
Myeloid Cells
Myeloid Cells: First line of defense, non-specific innate immunity
• Neutrophils
• Eosinophils
• Basophils/Mast cells
• Monocytes/Macrophages/Dendritic Cells
Lymphoid Cells
Lymphoid Cells: Humoral and Cell Mediated specific immunity
• B Lymphocytes
• T Lymphocytes
• Natural Killer Cells (innate immunity)
Bone marrow
• Site of hematopoiesis & B lymphocyte development
• is a loosely-organized group of cells in central soft tissue portion of bones surrounded by calcified matrix
• Hematopoietic stem cells- development of all blood cells after about the seventh month of gestation in humans
• B lymphocytes, granulocytes, monocytes and erythrocytes all develop to maturity in the bone marrow before they are released
• Pro T lymphocytes (immature T cells) are released into the bloodstream before final maturation
what structure of B cell
marker and its function
surface ig- antigen specific recognition
MHC , class II - Antigen presentation
B7-1 & 2- T cell activation
CD40- receives activation signal from t cells
CD19-21 - unique B cell markers
mitogen receptor - binding and activation by bacterial products
Activation of B Lymphocytes
Activation of B Lymphocytes
• Activation of B cells into antibody secreting cells is antigen-dependent.
• Specific antigen binds to surface Ig molecules which triggers differentiation into plasma cells.
• Interaction with T cell secreted factors triggers isotype (class) switching.
Clonal selection theory
Clonal selection theory
• Every individual has numerous clonally derived lymphocytes, each arising from a single precursor
• Each clone is capable of recognizing and responding to a distinct antigenic determinant
• Antigen selects a specific pre-existing clone and activates it, leading to proliferation and its differentiation into effector and memory cells
thymus
• Bilobed organ - site of T lymphocyte development
• 2 types of tissue - reticular cells(stromal cells) and developing T
lymphocytes (T cells) are randomly situated in clusters
• Cortex - area of intense T cell development. Pro T cells develop their antigen-receptors (TCRs) & their (CD4 & CD 8) co-receptors to become immature “double-positive” T lymphocytes
• Corticomedullary junction - region between cortex & medulla where self-responsive T cells are eliminated by apoptosis by interaction with antigen-presenting cells (APCs)
• Medulla -“staging” area where mature “single-positive” T lymphocytes migrate before being released
T Lymphocyte types
T Lymphocytes develop in thymus
• T helper cells (Th) can synthesize and secrete cytokines and function to regulate immune responses (both antibody and cell-mediated) when appropriately stimulated during immune responses
• T cytotoxic cells (Tc) are mature precursor cells that, as a result of a cell-mediated immune response, differentiate into cytotoxic T lymphocytes (CTL) which mediate cellular immunity vs virus-infected cells and tumor cells
Types of Helper T Cells
• Th1
– participate in CMI. They are essential for controlling such intracellular pathogens as viruses and certain bacteria, e.g., Listeria & M. tuberculosis
• Th2
– These provide help for B cells, are essential for antibody-mediated immunity. Antibodies are needed to control extracellular pathogens