Sunday, 31 October 2010

MRCP revision battle 38.2: B cell disorders

B cells are lymphocytes involved in humoral immunity.  Their functions are:
  • production of antibodies (=plasma B cells)
  • memory of antigen (=memory cells, live for a long time and able to respond rapidly if body encounters same antigen again)
  • antigen presenting cells

B cell disorders result in a failure of antibody synthesis, resulting in either hypogammaglobulinaemia or agammaglobulinaemia.  This causes recurrent infections with pyogenic bacteria and fungi.

Examples of B cell disorders include:

1. Common variable immunodeficiency
  • commonest cause of hypogammaglobulinaemia
  • not familial
  • bone marrow shows a normal number of B cells but they fail to mature

2. IgA deficiency
  • commonest isolated Ig in UK
  • increased risk of giardiasis

3. Bruton's agammaglobulinaemia
  • x-linked recessive
  • no circulating B cells
  • usually presents between 3 months and 2 yrs of age

Now on to the T cell disorders......