Apley & Solomon’s System of Orthopaedics and Trauma 10th edition (2018) PDF download
Apley & Solomon’s System of Orthopaedics and Trauma 10th edition (2018) PDF download B cells differentiate from lymphoid cells in the bone marrow in a way that allows them to express an antigen receptor on the surface
permanently. The expression of the receptor is a definition of B cells
and is a result of the differentiation pathway.
The antigen receptor varies from one immature B cell to another. There are billions of different receptors, but any B cell will express only one type of receptor.
The antigen does not ‘design’ the receptor; rather, a clonal B cell that
recognizes the antigen (very few B cells will recognize a given antigen) will proliferate in response to the antigen and signals from T cells.
As the B cells proliferate and differentiate further, the DNA region that codes for the antigen receptor undergoes mutation, and cells with mutations that recognize the antigen better are selected for further
development, while those that do not recognize the antigen die.
NFκB is a transcription factor that alters cell behaviour. It inhibits apoptosis and increases cell proliferation by increasing the production of tumour necrosis factor (TNF-α).
The following are the major patterns of deficiency:
● C3, C1q and factors H and I: susceptibility to capsulated bacteria, also
systemic lupus erythematosus (SLE)-like syndrome
● C5-9: susceptibility to disseminated neisserial infections
● C1 esterase deficiency: hereditary angio-oedema.