Lecture 18 - Immune and Lymphatic System Flashcards
What are innate immunity and acquired immunity?
L18 S4
Innate:
- lacks specificity
- results in inflammation
- primarily neutrophils
Acquired immunity:
- specific to antigens
- takes time to develop
- has specificity and memory
What are passive and active immunity?
L18 S4
Passive:
-temporary immunity due to donated antibodies (ie. transplacental antibodies)
Active:
-long-lasting immunity due to memory T cells and B cells specific to certain antigens
What are the different types of lymphoid tissue/organs?
What are the different types and what differentiates them?
L18 S6
Primary lymphoid tissue:
- thymus
- bone marrow
Secondary lymphoid tissue:
- lymph nodes
- spleen
- tonsils
Lymphocytes mature in primary lymphoid tissue and later reside in secondary lymphoid tissue
What are lymphoid follicles?
What are the different types and what differentiates them?
L18 S7
-transients sites of B cell localization and proliferation
Primary follicles:
- tightly packed accumulations of virgin B cells
- not yet exposed to antigens
Secondary follicles:
-derived from primary follicles that have been exposed to non-self antigens
Differentiate between diffuse and aggregated lymphoid tissue.
L18 S9
Diffuse:
- clusters of plasma cells, macrophages, and lymphocytes
- located in connective tissue
Aggregated:
-located beneath epithelium and is in direct contact with it
All immune cells originate in __________. T cells mature in __________ and B cells mature in __________.
L18 S11
Bone marrow; the thymus; bone marrow
What are MHCs?
What are the two types and how are they differentiated?
L18 S16
-present antigenic peptide to T cells
MHC I:
-expressed on all cells except trophoblasts and RBCs
MHC II:
-expressed on the surface of B cells and antigen presenting cells
What are the main types of T cells discussed and what differentiates them?
L18 S18-19
CD4+ T cells:
- helper cells
- assist in differentiation of CD8+ T cells and B cells
- recognize MHC class II molecules
CD8+ T cells:
- cytolytic T cells
- bind to antigen presenting cells and
- recognize MHC class I molecules
CD16+ T cells:
- natural killer (NK) cells
- activated by tumor cell antigens by releasing cytokines
Describe the process of T cell-mediated immunity.
L18 S22-23
- macrophage phagocytizes foreign material
- foreign proteins are broken down and present on cell surface my MHC II complex
- complex is bound by helper T cell
- helper T cell undergoes mitosis producing interleukin secreting cells and memory cells
- helper T cells attract B cells
- B cells undergo mitosis producing plasma cells which secrete antibodies or memory cells
Describe the classic pathway of the compliment cascade.
L18 S29-34
- C1q subunit binds to Fc portion of antigen bound antibody
- C1q activates C1r which then activates C1s
- C1s activates both C4 and C2 splitting them both into #a and #b
- 4b binds pathogen and 2b binds 4b (this is C3 convertase)
- C3 is activated splitting into 3a and 3b
- 3b binds 4b2b (this is C5 convertase)
- C5 is activated splitting into 5a and 5b
- 5b binds 4b2b3b resulting in opsonization of the pathogen
What role do 3a and 5a play once release by the compliment cascade?
L18 S34
-recruit leukocytes to site of infection
Differentiate parenchyma and stroma.
L18 S37
Parenchyma:
-cells that pack areas of lymphoid organs (typically leukocytes)
Stroma:
- reticular fibers and cells
- undifferentiated cells and free/mixed macrophages
Describe the histological features of a lymph node.
L18 S38-41
Hilus:
-entry and exit point for vessels
Capsule:
-dense collagen fibers with some elastic fiber and smooth muscle
Trabeculae:
-extensions of the capsule into the lymph node
Follicles:
- outer cortex
- contain B cells, follicular dendritic cells, and migrating dendritic cells
- secondary follicles contain mantle and germinal centers; primary do no
Medulla:
- loose medullary sinuses and dense medullary cords
- site of lymphocyte reentry
The thymus has __________ lymph vessels but not __________ vessels. This means lymph does not flow through the thymus.
L18 S51
Efferent; afferent
Describe the process through which a T cell differentiates.
L18 S54-55
Double negative T cells:
- lack surface molecules (CD4, CD8 and TCR)
- enter cortex from blood vessels
Double positive T cells:
-Express CD4, CD8 and TCR in response to epithelial cells present in the outer cortex
Single positive cell:
- lose expression of either CD4 or CD8 by binding to self-MHC molecule
- occurs in the medulla
