Dean Ostrander Jr., age 11, of Missoula, Mont., for his question:

WHAT IS GAMMA GLOBULIN?

Gamma globulin is a mixture of proteins in plasma, the fluid portion of blood. It contains antibodies produced in the liver, spleen, bone marrow and lymph glands to protect the body from invading viruses or bacteria.

Each disease antigen (invading protein) stimulates production of a specific antibody which circulates in the blood for a period of time. Since the gamma globulin contains these antibodies, it is sometimes taken from patients who have recovered from chicken pox, tetanus and hepatitis and given to confer a rapid but short term immunity on persons recently exposed to those diseases.

Persons who suffer from an unusual deficiency of gamma globulin known as agammaglobulinemia are deficient in antibodies and may require periodic infusion of gamma globulin to maintain protection.

In 1969 scientists in England and at Rockefeller University in New York City determined the chemical structure of gamma globulin, an important advance in knowledge of immunity.