T lymphocyte Activation in Tumor-free and Tumor-bearing individuals.

Natalia T Tuera, Erika A. Danna, Dr. Suzanne O.Rosenberg

Department Of Biological Sciences, UMBC, Baltimore, MD 21250.

Our lab is developing vaccines against metastatic cancer. Successful vaccination against cancer will require a host that has a fully competent immune system, capable of immunologically responding to tumor cells. Using the mouse 4T1 mammary carcinoma tumor model, we observed that B-cell response is suppressed in tumor-bearing mice resulting in immunocompromised host. We are currently examining T-cell responses to determine if they are also suppressed. There are two types of T cells: CD8⁺ and CD4⁺. CD8⁺ T cells destroy the tumors with the assistance of CD4⁺ T cells. We use IL-2, an important growth factor secreted by CD4+ T cells, as a standard to measure T-cell activity. Thus, we are comparing IL-2 production in mice with the 4T1 mammary carcinoma, versus mice with their primary tumor surgically removed, versus naïve (tumor-free) mice. Three weeks after tumor inoculation, the splenocytes are removed and assayed for T-cell activation using 3 different assays:

1. Coculture with SEB, a superantigen that binds to the T-cell receptor and MHC class II molecules, causing T cells to secrete IL-2.
2. Coculture with irradiated allogeneic (genetically different) lymphocytes in a mixed lymphocyte reaction (MLR). The MHC incompatibility between the stimulator and responder cells will cause the BALB/C lymphocytes to proliferate and secrete IL-2.
3. Incubation with anti-CD3 antibody that binds to the CD3 marker, which is present in all T cells, causing T-cell activation.

IL-2 production is measured using the sandwich ELISA method. To date, we have tested T cells from tumor-free mice and shown that they produce IL-2 in all assays. In future experiments, we will test T cells from tumor-bearing mice and post-surgery mice. The information gathered form these data will help us in understanding the immunological status of tumor bearing hosts, which will help us in deriving better vaccines against cancer.