Immune trait ups cervical cancer risk.

Certain inherited immune system proteins may boost the risk of developing cervical cancer after infection with a sexually transmitted virus.

It's well known that infection with certain types of human papillomavirus (HPV) can increase a woman's chances of developing cervical cancer. Yet no one knows why some women clear this virus with on apparent ill effects while others go on to develop a precancerous condition and even cancer of the cervix. Immunologist Raymond Apple of Roche Molecular Systems in Alamede, Calif., believes that the immune system may play a part in this sometimes deadly molecular game.

Apple's team analyzed tissue sampled from 318 women at high risk of cervical cancer. The group included 118 women previously diagnosed with the disease and 200 controls who did not suffer from it. The researchers obtained tissue either during a routine Pap smear or a biopsy. Using polymerase chain reaction, a technique for detecting minutes quantities of DNA, the researchers searched for DNA from different types of HPV in the samples.

They also conducted laboratory tests to determine what type of HLA proteins each woman produced. HLA proteins sit on the surface of certain immune cells and play a role in the body's recognition of and response to foreign tissue or a microbial invader, such as a virus. Each person inherits a genetic blueprint for a distinctive mix of HLA proteins.

Thne new study suggests that certain HLA protein may increase drastically the chance that a woman will suffer from cervical cancer if she if infected with HPV-16, a virus type associated with cervical cancer. In contrast, the findings hint that other HLA proteins may actually be protective. Certain HLA proteins may help the body clear HPV-16, while others lead to an ineffectual fight, thus increasing the risk that a cervical cell will become abnormal and eventually turn malignant, Apple speculates.