Severe Combined Immunodeficiency - The Story of Bubble Boy
Living inside a bubble - all of us do that in different ways, don’t we? Some of us don’t want to face the reality of life, some of us want to shut everything else out because we consider ourselves too superior or too inferior and some of us just simply like being alone and in our own world. So here is a story of someone like that. Someone who lived in a bubble - a literal one.
Why, you ask? Let me tell you his story.
David Vetter, born in Texas to David Joseph Vetter and Carol Ann Vetter, suffered from a primary immunodeficiency syndrome called severe combined immunodeficiency (SCID), right from birth. SCID is a hereditary disease which results in recurrent infections due to a non-functioning immune system. To understand the depth of SCID, let’s get down to the basics- The Immune System.
The human immune system is the one which defends us from germs and mico-organisms everyday. It protects us from millions of threats, both internal and external, each day. It acts by producing antibodies to act against the antigens entering the body. The Immune System provides immunity through two ways : Innate, which includes physical barriers, blood borne complementary proteins and phagocytes which are present from birth and Acquired which consists of the T lymphocyte and B lymphocyte mediated immunity.
To understand SCID, lets focus more on the acquired immunity. When a foreign antigen enters the body, the B cells bind to the antigen and initiate antibody response. These antibodies recognise the antigen and aid in the response against it which is mediated by the T cells.
T-cells are further divided into three types :
Cytotoxic T cells which kill the invading organisms
Memory T cells which remembers the antigen and can make the immune response quicker on subsequent exposure.
Helper T cells which assist the B-Lymphocytes.
In severe combined immunodeficiency, the T and B lymphocytes are not properly synthesised. In some rare cases the natural killer cells or NK cells are also absent. These three cells - NK cells and B and T lymphocytes are of paramount importance for the immune system to function properly because without these the body would be incapable of recognising foreign antigens and also of removing them from. our body.
So how does the body manage to get itself into such a mess. Well you see, all blood cells arise from a single precurssor cell known as the hematopoietic stem cell. Now this stem cell, through the influence of various messengers differentiates itself into different lineages. Broadly all the white blood cells in the body can be divided into myeloid and lymphoid lineages. T cells and B cells arise from a common lymphoid progenitor, as do NK cells. Now for the progenitor cells to get differentiated into these various lineages and further differentiate into cells with special functions certain messengers called interleukins are needed.
In SCID, genetic mutations hamper with the synthesis of these interleukins. The commonly affected interleukins are : IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21. Each of these interleukins has a specific function.
IL-2 is necessary for the multiplication of T cells.
IL-4 is responsible for B cells to produce various types of antibodies.
IL-7 causes apoptosis which is essential in getting rid of certain unwanted T cells in the thymus.
IL-15 is needed for NK cell development.
So when these interleukins are lost, the whole system designed to protect our body isn’t properly formed, leaving our body defenceless. So what happens then? Lets go back to David Vetter.
David Vetter grew up with utmost care right from birth. Immediately after he was born he entered his bubble- a plastic germ free environment. He was exposed to the outside world only for a mere 20 seconds! From then on, he lived only in the bubble. Food, clothes and other items were sterilised beforehand and sent into the bubble.
When he was six, he could step outside for the first time, thanks to NASA who created a special spacesuit for him. A TV area and play area were added later on to his bubble. He acquired his education too, as he came of age- everything through the bubble.
This is how life went on for David. He couldn’t get a suitable donor for a bone marrow transplant for a very long time. A lot of ethical issues arised, concerning him –growing a child inside a closed space and the mental agony that he was put through. All this went on until David was 12 years old. He finally got a bone marrow transplant from his sister, Katherine. But this wasn’t a happy ending for David. A latent strain of Epstein Barr Virus had been introduced into his body through the marrow transplant which resulted in Burkitt’s Lymphoma (a type of cancer of the lymphatic system). David passed away 4 months later.
This is probably one of the most unfortunate stories that we’ll come across in the field of medicine. But David’s case served as a milestone for SCID. There have been developments in gene therapy, hematopoietic stem cell transplantation and enzyme replacement therapy. Well, every cloud has a silver lining and David was the silver lining for thousands of people who suffered from SCID in the upcoming years. His story gives us a ray of hope and shows extreme amounts of resilience displayed by a 12 year old boy. Its definitely something to look up to in this day and age.
Author: Sw. Kopiga Sree