Flashcards in Jitt # 10 CD40 Ligand Deficiency Deck (13):
After recognizing an antigen, what is the first antibody to appear?
What antibodies predominate in the serum and extravascular spaces?
What type of antibody is present in the gut and respiratory tract?
Where is IgE produced?
In the mucosal tissues
What type of cells undergoes class switching? How is class switching induced?
B cells, induced by T cells (T cell dependent)
How is T cell independent class switching induced?
Induced when microbial antigens or repeated epitopes are recognized by TLRs
How is T cell dependent class switching induced?
T cells express CD40L, B cells have CD40 R when activated, both bind together; T cells secrete cytokines to help B cells grow and proliferate. B cells are activated when T cells recognize antigens on B cells in the context of MHC
What cytokine is important for the production of IgE?
CD40L gene and consequence of mutation
CD40LG; located on the X chromosome at Xq26; people who have a mutation in this gene are only able to produce IgM or IgD and are unable to switch to other Ig sub classes; Disease, Hyper IgM syndrome, CD40 deficiency,
On what cells are CD40 expressed?
Macrophages, DCs, FDCs, Mast cells and some epithelial and endothelial cells. In CD40 deficiency cases, there is no interaction between these APCs and the T cells. Antigen specific T cells are produced in very low numbers.
Characteristics of CD40L Deficiency
Low WBC count, severe neutropenia (causes sores and blisters in the mouth), normal levels of lymphocytes, High number of monocytes, absence of secondary follicles and germinal centers; recurrent infection with pyogenic bacteria; Can make antibodies for T- Cell independent bacteria, but cannot make antibodies against T cell dependent antigens; also have defects in cell mediated immunity (No T cell activation of Macrophages); persistent inflammation of the liver (leads to liver failure);
How do you treat severe neutropenia?
G-CSF; granulocyte colony stimulating factor