I think 31 kDa, and esspecially 41 kDa DOES cross react with other bacteria and viruses. On the Igenex website, there is a new test that they have that can help differentiate if your 31 kDa is specifically from Lyme or if it's from another bacteria.
I actually had similar results on my test... I had 31 IND, 39 IND, and 41 ++. I also had a 58 +. But then my results went more negative with time... Down to just 39 IND, and 41 +. I think 58 is from bartonella but I don't know for sure... Some of these bands on the Lyme Igenex are also from co-infections. 41 kDa, maybe common in many bacteria and viruses... and for some reason when we get really sick it shows. It is common because it is for bacteria flagella, and many bacteria esspecially pathogenic bacteria have flagellas.
I think the others are right though with the INDs... It means there is a mild and weak immune response, but it is suggested sometimes that they can potentially be negative and have in the past.