Histo - Lymphoid Flashcards
(35 cards)
What are the 4 types of Immunity?
-
Cell-mediated (adaptive)
- Mostly T lymphocytes
-
Humoral (adaptive)
- B-lymphocytes & Plasma Cells
-
Innate (not adaptive)
- Macrophages, granulocytes, & natural killer cells
- Epithelia & complement system
-
Passive Immunity
- maternal antibodies
- from placenta & milk
- maternal antibodies
What are the 2 types of Lymphoid Organs?
-
Primary
-
Bone marrow
- B & T cells formed here
- B cells mature here
-
Thymus
- T cells mature here
-
Bone marrow
-
Secondary
- Lymph nodes
- Spleen
-
Diffuse lymphoid tissue of mucosa of GI
- Tonsils
- Peyer’s Patches
- Appendix
-
Mucosa-associated lymphoid tissue (MALT)
- GI
- Respiratory
- Urinary
How is lymph transported?
-
Lymphatic vessels
- transport interstitial fluid (lymph) to blood
- Lymphoid organs
- immune cells within
- primary & secondary

What are the characteristics of Innate Immunity and 3 associated cells?
Basics:
- Immediate & NON-specifc
- Physical barriers & Cells
Cells:
-
Leukocytes (WBCs)
- Toll-like receptors on leukocytes
- Granular
- Basophil, Eosinophil, Neutrophil
- Agranular
- Monocyte/Macrophage & NK cells
- Mast Cells
-
Dendritic cells
- Ag presenting cells
Anti-microbial chemicals:
- Acids
- Defensins
- Lysozymes
- Complement
- Interferons
What are the characteristics of Adaptive Immunity and 3 associated cells?
Basics:
- SLOWER than innate response
- More SPECIFIC than innate response
- Ability to recognize Antigens
- cause cell response
Cells:
- B-cells
- T-cells
- Ag presenting cells
- help B & T cells
- part of mononuclear phagocyte system
Note:
-
Memory lymphocytes = remember response
- lead to faster response in future contact w/ Ag
- basis for vaccine
What are the 2 major structural components in this image?
-
Stroma of Lymphoid Organs
- CT framework
- Reticular fibers
-
Parenchyma of Lympoid Organs
- Immune cells
- Functional part of organ
What is this?

Reticular Fibers
- Part of Stroma of Lymphoid Organs
- Stain w/ Silver
What is this?

Immune Cells
- Part of Parenchyma of Lymphoid Organs
- ONLY immune cells visible
- Functional part of organ
Note:
- No stained reticular fibers in this image
What are the 3 types of Lymphocytes?
Adaptive Immunity:
-
T-lymphocytes
- Helper T, cytotoxic T, Regulatory/Suppresor T, Memory T
- Mature in Thymus –> Secondary lymphoid organs
-
B-lymphocytes
- Plasma cells & Memory B cells
- Mature in Bone Marrow –> Secondary lymphoid organs
Innate Immunity:
- Natural Killer (NK) cells
NOTE:
- All derive from Lymphoblast in Bone Marrow

What is this?
T Lymphocytes
- Found a_bundantly in GI tract_
- basophilic & round nuclei
- Cannot quite distinguish from B cells
What is DiGeorge Syndrome?
Basics:
- Thymic aplasia = messed up thymus
-
NO T cells
- no cell-mediated response to Ags
- ONLY B cells
Treatment:
- Thymic transplant = ideal option
What is Agammaglobulinemia & Hypogammaglobulinemia?
Agammaglobulinemia:
-
NO B cells
- no plasma cells & no Abs
-
ONLY T cells
- cell-mediated response
Hypogammaglobulinemia
-
SOME B cells
- Reduced Ab production
- T cells present
What is Severe combined immunodeficiency disease (SCID)?
Basics:
- AKA: Adenosine Deaminase Deficiency or Bubble Boy Disease
- NO T cell & NO B cells
- Innate Immunity ONLY
What is the different between the 2 types of Lymphoid organs?
-
Primary
-
Initial location of maturing lymphocytes
- Bone Marrow
- Thymus
-
Initial location of maturing lymphocytes
-
Secondary
-
Where immune response happens
- Tonsils
- Peyer’s Patches
- Veriform Appendix
- Lymph nodes
- Spleen
-
Where immune response happens
What is the difference between images?
Thymus of Child (Left) & Thymus of Adult (Right)
Basics of Thymus:
- Efferent lymphatic drainage ONLY
- Site of T cell maturation
Structure:
- Thymic lobes w/ CT capsule
- Lobes separated by septae
- Lobules have cortex & medulla
Child vs. Adult:
- Child = large; Lots of differentiation of T cells
- Adult = small; Lots of fat & loss of tissue
What are the 2 major structures in this image?

Cortex & Medulla of Thymus
Cortex:
-
T-cells = MORE than medulla
- darker stain
- Epithelial reticular cells = FEWER than medulla
Medulla
- T-cells = LESS than cortex
-
Epithelial reticular cells = MORE than cortex
- __lighter stain
-
Hassall’s Corpuscles
- Wholes of epithelial reticular cells
- Enlarge w/ age
- ** helps us ID the thymus**
What is this?
Medulla of Thymus
-
T-cells
- small, dark nucleus
-
Reticular epithelial cells
- larger, more clear/eosinophilic
-
Hassalls Corpuscles
- LARGEST, most eosinophilic;
- nuclei similar to reticular epitheial cells
What is the Blood-Thymus Barrier?
Basics:
-
Dual Basal Lamina
-
Reticular epithelial cells
- linked by desmosomes
-
Endothelial cells
- continous capillary
-
Reticular epithelial cells
-
Macrophages
- proximity = help to protect dev. T cells
Note:
- Together, blood-thymus barrier + Macrophages = protect dev. T cells
What is this?

Cortex of the Thymus
-
Epithelial reticular cells
- linked by desmosomes
- larger; clear cells
-
T lymphocytes
- smaller; basophilic
What is this?

Medulla of the Thymus
-
Less T cells
- small, basophilic
-
More reticular epithelial cells
- larger, clearish, eosinophilic
-
Hassall Corpuscles
- largest, very eosinophilic
Where are Mucosa-Associated Lymphoid Tissue (MALT) located?
Mucosa-Associated Lymphoid Tissue (MALT)
Systems:
- GI
- Respiratory
- Urinary
- All = open to outside
- potential sites for pathogen entry
- All = open to outside
Locations:
- Diffuse lymphoid tissue
- Lymphoid nodules
- Tonsils
- Peyer’s Patches
- Appendix
What is this?
Diffuse Lymphoid Tissue in Esophagus
-
Lymphocytes in CT
- not making a formal structure yet
- In Lamina Propria
What is this?
Lymphoid Nodules in Esophagus
2 Parts of Lymphoid Nodules
-
Primary
- Cluster of tightly packed cells
- Mostly B cells
-
Secondary
-
Corona (mantle)
- new lymphocytes
- darker outer region
-
Germinal center
- B cell proliferation
- B cell differentiation
- May contain T cells & APCs
- central lighter region
-
Corona (mantle)
What are the 3 types of Tonsils?
-
Pharyngeal tonsils
- single
- wall of nasopharynx
- covered by pseudostratified columnar epithelium
-
NO crypts
- if inflammed & hypertrophied = “adenoids”
-
Lingual tonsils
- base of tongue
- numerous
- covered w/ SSNK epithelium
- SINGLE crypt
-
Palatine tonsils
- paired
- in wall of oropharynx
- covered by SSNK epithelium
- SEVERAL crypts





