A powerful immune system might not sound as enticing as six pack abs, but in the long run it's probably more important in scoring with the opposite sex. A new study has found that women largely rely on testosterone levels to tell which male is the healthiest person to procreate with.

According to LiveScience, researchers recruited 74 Latvian men in their early-20s before injecting them with a Hepatitis B vaccine to triggers their immune system and create antibodies to fight the virus. They then took blood samples right before and one month after the first dose of the vaccine was given and measured antibody levels, levels of testosterone and the stress hormone cortisol. The researchers also showed photographs of each man to 94 Latvian women (all in their 20s) and had them rate the pictures on a 10-point scale of attractiveness.

By analyzing the men's immune response and hormone levels in connection with their attractiveness score, the researchers concluded that high testosterone correlated with both sexy faces and a strong immune response. While testosterone has been linked to attractive masculine facial features, what's interesting is that men who had the strongest immune responses were perceived as better looking than those with the weakest. Additionally, the connection between testosterone and attractiveness was the strongest in men who had the lowest levels of cortisol (which is linked to stress).

So keep in mind that when you're looking to score a date, it's antibodies and not hard-bodies that's more likely to get you laid.