HYPER IgM SYNDROMES

Question 1

What happens in Hyper IgM syndrome

Answer 1

B-cells cannot undergo antibody class switching
↳ They have a lot of IgM antibodies but no other antibodies

Question 2

What is the deficiency in Hyper IgM syndrome

Answer 2

CD40L (CD154) deficiency leads to abnormal interaction with B cell that express CD40 receptors

Question 3

In the absence of CD154 what happens?

Answer 3

B cells can express IgM but have difficulty switching and are likely to undergo apoptosis rather than proliferate

Question 4

Type 1 CD40L (CD154) deficiency

Answer 4

-X linked recessive
-Mutation in CD40 ligand gene
-T cells can´t activate B cells

Question 5

Clinical features

Answer 5

-Reduced serum concentration IgG, IgA, IgE
-Normal elevated amount of IgM, normal circulating B cells
-No germinal centers in lymph nodes
-Recurrent upper and lower respiratory infections