Their brains may provide antibiotics.

http://www.nottingham.ac.uk/News/pressreleases/2010/September/CockroachAntibiotics.aspx

The underlying paper is probably

"The brain lysates of locusts and cockroaches exhibit

potent broad spectrum antibacterial activity", Simon Lee et al.

But they are also carriers of superbugs.

http://phys.org/news/2011-01-superbugs-swine-antibiotic-resistant-bacteria-flies.html

Regards,

Joachim

thank you Mr.Pimiskern

The scientific work of the French Nobel Price Jules Hofman is on the innate immunology of insects. Please look at :

http://idw-online.de/pages/de/news237418

Regards, Gerard

The insects are known to possess innate immunity...

The humoral component of innate immunity includes secretion of anti-microbial peptides, such as defensins and cecropins... These small peptides are indeed anti-bacterials...

usually innate immunity is considered to lack specificity and memory, however, the larger insects, like cockroaches do have a degree of memory in them.