A couple of minor points.

I was puzzled by the comment "This impaired immunity is in the endocrine system, but not so much in the nervous system." This doesn't make any sense and suggests a fair bit of confusion over our bodies internal workings.

The immune system, the endocrine system and the nervous system are separate systems with distinct functions in the mammalian body. Roughly speaking, the endocrine system is made up of glands that produce hormones, the hormones themselves and the tissues to that respond to them. The nervous system is the network of nerves that communicate rapidly between different parts of our body and do the complicated processing jobs in our spinal cords and brains. The immune system is the collection of cells involved in fighting infection and hunting down aberant, potentially cancerous cells in our bodies.

These three systems do talk to each other but I do not understand how an immune deficiency can be "in the endocrine system, but not so much in the nervous system".

The best analogy I can come up with is to think of the nervous system as the Internet, the hormone system as the mail service and the immune system as the police. They all depend on each other to some extent but if you have a problem that eliminates your police force, then it is not going to appear more in the mail than the Internet.

Also the description of X-linked SCID as a defect in the adenosine deaminase, ADA, enzyme is wrong. Technically, X-linked SCID is a defect in the IL2RG gene which results in, amongst other things, a lack of T cells. The ADA gene defect is autosomal recessive, which means that someone has to inherit two copies of the faulty gene, one from each parent. It is not X-linked which means both sexes are equally prone and results in a deficiency of both B and T cells.