Gene Therapy: Bursting the Bubble on SCIDs

Glossary

Antibody
A soluble protein molecule produced and secreted by B cells in response to an antigen, which is capable of binding to that specific antigen.

Antigen
Any substance that, when introduced into that body, is recognized by the immune system.

B cells
Small white blood cells crucial to the immune defenses. Also known as B lymphocytes, they are derived from bone marrow and develop into plasma cells that are the source of anitobodies.

Bone marrow
Soft tissue located in the cavities of the bones. The bone marrow is the source of all blood cells.

Cellular response
The immune response of the body represented by the T cells of the immune system.

Cytokines
Powerful chemical substances secreted by cells. Cytokines include lymphokines produced by lymphocytes and monokines produced by monocytes and macrophages.

Cytotoxic T cells
A subset of T lymphocytes that can kill body cells infected by viruses or transformed by cancer.

Ex vivo
A gene therapy technique in which the DNA of a person is removed, altered in a laboratory test-tube, and then returned to an individual.

Granulocytes
White blood cells filled with granules containing potent chemicals that allow the cells to digest microorganisms, or to produce inflammatory reactions. Neutrophils, eosinophils, and basophils are examples of granulocytes.

Helper T cells
A subset of T cells that typically carry the T4 marker and are essential for activating antibody production, cytotoxic T cells, and initiating many other immune responses.

Humoral immunity
Immune protection provided by soluble factors wuch as antibodies, which circulate in the body's fluids or "humors," primarily serum and lymph.

Immune response
The reactions of the immune system to foreign substances.

Immunoglobulins
A family of large protein molecules, also known as antibodies.

Immunosuppression
Reduction of the immune responses, for instance by giving drugs to prevent transplant rejection.

Interleukins
A major group of lymphokines and monokines.

Lymphocytes
Small white blood cells produced in the lymphoid organs and paramount in the immune defenses.

Monocyte
A large phagocytic white blood cell which, when it enters tissue, develops into a macrophage.

Natural killer (NK) cells
Large granule-filled lymphocytes that take on tumor cells and infected body cells. They known as "natural" killers because they attack without first having to recognize specific antigens.

PCR
Polymerase Chain Reaction. A technique for the rapid production of millions of copies of a particular stretch of DNA.

Severe combined immunodeficiency disease (SCID)
A life-threatening condition in which infants are born lacking all major immune defenses.

T cells
Small white blood cells that orchestrate and/or directly participate in the immune defenses. Also known as T lyphocytes, they are processed in the thymus and secrete lymphokines.

Eligibility for the Ex-Vivo Gene Therapy Trial

Both patients P1 aged 11 months and P2 aged 8 months did not have a bone marrow matched sibling.
Although P1 expressed the gamma-c receptor on the membrane, the receptor lacked the tail needed for communication. Thus, the gamma-c receptor, although present was functionless.
P2 did not express the protein at all.

Procedure

Both patients were placed in a sterile isolation ward. They received oral antibiotics and intravenous immunoglobulins every 3 weeks for 3 months.
CD34+ cells from their bone marrow were harvested.
After CD34+ cell separation, the cells were infected with the MFG gamma-c vector daily for 3 days.
These cells were then given back to the patients.

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