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Plugging up leukemia cells.

Plugging up leukemia cells

As scientists learn more about the immune system, they are developing sharper tools for manipulating it. At the Sixth International Congress of Immunology in Toronto earlier this month, Thomas A. Waldmann of the National Cancer Institute (NCIe in Bethesda, Md., described the use of an antibody that specifically targets only active forms of T cells, one of the two types of lymphocyctes that make up the immune system. In experimental use against adult T cell leukemia, the agent caused temporary remission; Waldmann hopes it will eventually be useful in other T-cell-related conditions as well.

Each T cell is sensitive to a specific foreign antigen. to generate enough T cells to mount a defense, a T cell that has "seen" its target antigen initiates the cloning process in two ways--by producing interleukin-2, which stimulates T cell division, and by manufacturing specific cell-surface receptors for interleukin-2, making the T cell more sensitive to its presence.

Interleukin-2 can be helpful therapeutically. Steven A. Rosenberg and his colleagues at NCI have had initial success in using it to stimulate immune cells to fight cancer (SN:12/7/85,p.359). But in adult T cell leukemia, naturally produced interleukin-2 promotes an eventually fatal proliferation of T cells.

Waldmann and his colleagues injected five patients with an antibody to the interleukin-2 receptor in order to block its cell-stimulating effect. Since the interleukin-2 receptor appears only on activated T cells, including the leukemic cells, the antibody leaves the rest of the immune system alone. The treatment initially worked in two patients but, for undetermined reasons, eventually wore off. None of the patients had any side effects. As a next step, the researchers have just begun animal trials with a toxin-armed antibody aimed at killing the leukemic cells rather than just blocking their division.

"I think [the antibody] treatment has much broader ramifications," Waldmann says. T cells are also at fault in other conditions, such as transplant rejection and diseases marked by the immune system mistaking normal tissue as foreign; the antibody, he suggests, might prove useful in these cases.
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Author:Silberner, Joanne
Publication:Science News
Date:Jul 26, 1986
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