OUR BODIES, OUR MINDS..

by

Harvey Thompson, M.D. "A Layman's Guide to

the Innune Systen" Antigon, antibody, lymphocytes, cellular immunity, suppressor and helper cells: sound like a Christmas shopping list for a blood bank? Maybe, but now that 80% of even healthy Gay males have been shown to be immuno-suppressed, interest in these terms may soon rival the rush for tickets to a Bette Midler concert. Understanding the immune system is not easy. What follows is a short course to help you understand the findings of the research that's unfolding on the acquired immunodeficiency syndrone of Gay men (AIDS). You might remember looking at a blood smear in high-school biology and seeing white corpuscles. You vore told that they were phagocytes which, like vacuum cleaners, digested foreign bodies and cleansed the body. But what were those other round cells without cytoplasmic granules that comprised about a third of the white cello?

They were lymphocytes, and those are taking center stage in the current AIDS epidemic.

The source of the immune system are primitive undifferentiated cells found in the fetal yoke sac at about 4-5 wooks gestation. They take separate paths at about that time; some migrate through the thymus gland, and are therefore called "T" colle. Then they continuously recirculate between lymphoid tissues and bloodstream. The lymphoid tissue you're most familiar with are the swollen. and tender glands you feel under the angle of your jau when you get a sore throat. Normally, lymph nodes

are not swollen in their common locations of neck, armpits and groin. The spleen is a kind of giant-of-anode in the upper left corner of the abdomen.

The remaining undifferentiated cells, those that didn't take the trip through the thymus, become "8" cells, named after the "bursa" of birds, where they were first recognized. They go on to take up resid-

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ence in the bone marrow and the blood.

There are two major divisions of the immune system: the humoral and the cellular. The humoral, or fluid portion, is characterized by "antibody" production from the offspring of the "8" cells, blood plasma, in reaction to a foreign protein, or "antigen". Although "T" cells have a regulatory influence on "8" cell antibody production, they mainly comprise the second immune system division: the cellular or cell-mediated portion.

You know the humoral system because of its control of bacterial infections. The cellular system, on the other hand, is mostly responsible for control of mutant cancer cells and infections by virus, fungus, and tuberculosis-related organions. This latter group of "antigens" is the one that the Gay community seems to be having problems with.

An example of humoral system production is the antibody that fallous a tetanus shot of toxin (the "antisen") and lingers to neutralize the toxin from an accidental rusty-nail puncture years later. Cellular immunity is produced at the T8 skin test site when it is positive; over the next few days, lymphocytes are soon at the spot.

There are six major immune effector mechanisms, or ways in which the body reacts to protect itself from invasson. Four of these involve "8" cells and an antibody, but two are "T"cell mediated. All of these can be illustrated with the example of a snake crawling into a chicken coop: the snake is the foreign toxin or antigen, and the chickens determine the insune response.

First, some chickens would go into shock and die, just from contact with the snake. This represents a Type I or anaphylactic shock reaction, similar to what happens in some people with a lifethreatening penicil lin reaction.

Some chickens might innobilize the anake by holding it still (the noutralizing reaction). Other chickens might scrtach the snake and wait for ito alcu oozing to death. Their claus are what is called a "compli ment" in immunological torna, and this is a Type II reaction.

Some chickens would cackle loud enough to call Farmer White with his corpuscles to destroy the snakea Type III or Arthus reaction. But the cleverest chicken has a Type IV response; he just ingests the snake, and this is analogous to the "Killer T-cell response of cellular insty.

Type I, II, and III reactions, and the neutralizing response, represent antibody-mediated reactions of the humoral system, hoes of the "B"cells. Swallowing the snake demonstrates "T"-lymphocyte cellular immunity. The "antigon" (the snake) can either be digested (a Type IV reaction siilar to the T8 trine test), or just held in the stomach intact (granuloma formation similar to leprosy).

There's a connection between the "T" cells and the "8" cells of the two different systems, though. Romosber that I mentioned a feu paragraphs ago that T cells have a regulatory influence on the antibody production of the humoral system? There are two kinds of "T" cells, and they've gotten a lot of press lately. They're called "suppressor" and "helper" subsots. "Helper" T cells assist the "g" cells in producing antibodies; "suppressor T cells antagonize the "helpers" and limit antibody production in the humoral system.

It's just this systen of checks and balances that seems to be out of whack in the Gay male. We have, often, feuor "helpor" cells and more "suppressors" than normal. The ratio of helper to suppressor is decreased. You may hear your Gay friends discussing this ratio; it's currently a focal point of much investigation. However, the helper cell and absolute lymphocyte count may be more import-

ant.

You might expect that with fover

helper cells there would be less antibody production, but such is not the case. Instead, there is more antibody production (hypergammaglobulinemia) with elevated antirival antibodies. This unexplained paradox could result from faulty "T" cell suppressor activity or a high level of imeuno stimulation in a kind of "rebound" from that suppression.

With this background, you can conJecture all kinds of explanations for the appearance of AIDS in the Gay community. Since T cells are important in cancer cell surveillance, the final answer will probably also explain Kaposi's syndrome, the Gay

cancer.

SOME POSSIBLE EXPLANATIONS

Many viruses (cytomegalovirus, Hopatitis-8, and the Epstein-Barr virus of mononucleosis) cause T cell inbal ancos similar to those seen in AIDS. Perhaps this high level of immuno stimulation from one infection after another so overwhelming a suppressor regulation. Or, is ther an unknown virus that accounts for the illness? This seone likely, since some of the patients have had sexual contact with one another. Many investigators bolieve such a yet-undetected virus has a mode of trananiasion similar to Hepatitta-8. That would explain why Kaopsi's sarcoma is also occurring anong Haitians (whose country is endonic for Hepatitis-8), drug addicts and Gays (with a high incidence of Hepatitis-8), and homophiliacs (who are exposed to Hepatitis-8 from blood product transfusions).

In cancer, the rapid growth of malignant cells soong to outstrip T cell capacity to ingest tumor cells. AIDS and Kaposi's patients have decreased skin test responses; does this T cell sickness of the cellular inmuna syatom parait tumor cells to escape "killer" colla?

Is there a genetic predisposition to inmune defects which allows tumors to grow? Patients with Kaposi's sarcona share certain configurations in their human histocompatibility coplexes (Human Leukocyte Locus A, or HLA or short

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