Oral Tolerance Flashcards
Tolerance
State of unresponsive ness of the immune system to substances or tissues that have the capacity to elicit an immune response. This allows health; failure of tolerance leads to immune mediated issues.
3 types of tolerance
Self-tolerance
Neonatal tolerance
Oral tolerance
Self-tolerance
Prevents damage to self by auto reactive T and B cells
Occurs via central tolerance in thymus and peripheral tolerance elsewhere
Neonatal tolerance
Survival of the foetus and placenta within the pregnant mother
Occurs via peripheral tolerance (repro system)
Central tolerance
Selection of T and B cells which only react to non-self antigens in the thymus and bone marrow
Self-reactive lymphocytes are eliminated
Positive selection of T cells (Central tolerance)
T cells which recognise the body’s own MHC (I and II) are retained
Negative selection of T cells (Central tolerance)
T cells which respond to self peptides in the MHC are eliminated —> T cells which ignore self peptides are retained.
This is self-tolerance.
How is central tolerance induced in B cells?
Induced in bone marrow where Strom a, cells support B cell development. This is where B cell receptor (BCR) and immunoglobulin (Ig) are acquired.
BCR+ cells that interact with self-antigens on stromal cells undergo apoptosis
Mature educated B lymphocytes move to populate secondary lymphoid organs (adaptive immune response repertoire)
Most antigens are T cell dependent, so the induction of T cell tolerance will lead to B cell tolerance.
How are lymphocytes recruited to peripheral lymphatic organs? E.g. GALT
Lymphocytes leave LN, enter blood, then emigrate back from capillaries to intestine
Addressing on high endothelial venules interact with homing receptors on lymphocytes to ensure they reach the mucosal surface
In the end there is a high concentration of lymphocytes in this region; 70% of Ig-producing cells are found in the mucosal surfaces of the body.
Describe how peripheral tolerance is achieved
T and B cells in the secondary lymphoid tissues (peripheral lymphoid tissues) require further education and regulation
T cells are regulated outside the thymus in the peripheral organs and tissues e.g. MALT, GALT, local lymph nodes
When self-reactive T cells escape into the periphery, peripheral tolerance ensures they are deleted or be one anergic.
Anergic: functionally unresponsive to the antigen.
Failure of these mechanisms will result in hypersensitivity/allergic responses.
T cell tolerance occurs via which of the following:
Central tolerance
Peripheral tolerance
Both central and peripheral tolerance
Both central and peripheral tolerance
Oral tolerance occurs via which of the following:
Central tolerance
Peripheral tolerance
Both central and peripheral tolerance
Peripheral tolerance
B cell self-tolerance occurs in which area(s)
Thymus
Bone marrow
Peripheral lymph nodes
Bone marrow
What are the 3 routes whereby soluble and particulate antigens can be sampled from the gut?
Dendritic cell route
M cell route
Epithelial cell route
Describe the dendritic cell route of antigen sampling from the gut
Dendritic cells extend processes through the epithelium and into the lumen to sample particulate antigens
Describe the M cell route of sampling antigens from the gut
M cells overlying Peyer’s patches take up particulate antigens and deliver them to subepithelial dendritic cells
Describe the epithelial cell route of sampling antigens from the gut
Soluble antigens possibly cross the epithelium through trans cellular and parra cellular routes to encounter T cells or macrophages in the lamina propria
How are soluble antigens sampled in the gut?
A) via the dendritic cell route
B) via the M cell route
C) via the epithelial cell route
C) via the epithelial cell route
