Question

A five-year-old male patient was admitted to the hospital with a severe acute infection of the ethmoid sinuses. The patient has had a history of sinus infections. At three years of age, the patient had been diagnosed with a pneumonia infection, but did not have an increased level of white blood cells. Presently, the patient was treated with antibiotics and his antibodies against streptolysin O, an antigen from streptococci, were measured. The patient had no antibodies against SLO, and his IgG levels were low, IgA were undetectable, and his IgM levels were elevated. A biopsy was done of a lymph node and no secondary follicles or germinal centers were found. The patient was given a DPT vaccination, and no antibodies against the tetanus toxoid were generated as a result. When the patient’s cells were analyzed by flow cytometry, his CD19+ B cells stained positive for surface IgM and IgD, but not IgA or IgG. His T cells were isolated and stimulated in the lab with phorbol ester and ionomycin, but they did not bind CD40. There was no family history of susceptibility to infection. What deficiency does this patient suffer from?

Answer 1

there is deficiency of CD40 ligand

The CD40LG gene provides instructions for making a protein called CD40 ligand, which is found on the surface of immune system cells known as T cells. CD40 ligand attaches like a key in a lock to its receptor protein, CD40, which is located on the surface of immune system cells known as B cells. B cells are involved in the production of proteins called antibodies or immunoglobulins that help protect the body against infection. There are several classes of antibodies, and each one has a different function in the immune system. B cells are able to mature into the cells that produce immunoglobulin M (IgM) without any signals from other cells. In order for B cells to mature into the cells that produce antibodies of a different class, the CD40 receptor must interact with CD40 ligand. When these two proteins are connected, they trigger a series of chemical signals that instruct the B cell to start making immunoglobulin G (IgG), immunoglobulin A (IgA), and immunoglobulin E (IgE).

So thus if there is deficiency of CD40 cells will not be able to form other class of antibodies except Ig M which it can forms on it's own

That's why here also there is increase in IgM & decrease or absence of other class of antibodies