Immune cells and organs Flashcards
What is the general structure of the thymus gland?
Bi-lobed. Lobes are divided into lobules by septa. You get darker staining at the peripheries. You find hassall’s corpuscles that give rise to regulatory T lymphocytes.
How does the thymus change during infection?
It doesn’t
How does the thymus change with age?
The thymus gets smaller with age and thymic output decreases. More fatty tissue in the thymus.
How does the T cell repertoire in your body change as you grow older?
The number of T cells stays the same but the variety decreases. It becomes oligoclonal. There are more memory cells.
What are the names of lymphatic vessels that bring lymph to and from the lymph nodes?
Afferent – in; efferent - out
What are germinal centers and what do they indicate?
Germinal centers are accumulations of B cells – the germinal centers indicate the presence of on-going infection
Where do lymphocytes exit the circulation and enter tissues?
High endothelial venules
What is the immunological role of the spleen?
It filters the blood for antigens
Describe the organisation of lymphoid tissue around the arteries in the spleen.
White pulp (lymphocyte area) is right next to arteries. PALS (periarterial lymphatic sheath) is directly around the arteries and the B cell zone is beyond that. Germinal centers can form in the spleen as well.
What is a Peyer’s patch and what does it do?
Peyer’s patches are aggregates of lymphocytes found just below the intestinal epithelium. M cells in the epithelial layer sample antigens from the gut and deliver it to lymphocytes in the Peyer’s patch.
Which immune cells are found in the subcutaneous immune system?
Dendritic cells – Langerhans cells
Keratinocytes
Tissue resident macrophages
T Lymphocytes
What are the three receptor interactions involved in the extravasation of lymphocytes?
Selectin binding – weak interaction
Chemokine receptor binds to chemokine on the endothelial surface
Integrins on the lymphocytes bind to ICAM-1
Describe the sequence of events that occur when lymphocytes move out of the circulation.
The lymphocytes are initially rolling along the endothelial layer – selectins bind and slow down the rolling
Then the chemokine receptor on the lymphocyte will bind to the chemokine on the endothelial layer.
When the chemokine binds, the integrin will be changed to the high affinity state allowing it to bind with ICAM-1
What receptors do all T cells have?
CD3
What other types of receptor do T cells have?
90% of T cells have alpha-beta receptors and 10% have gamma-delta
Of the alpha-beta receptors: 2/3 have CD4 and 1/3 have CD8
