As I said, I decided to switch from one area of research to another and the natural bridge to the area that I decided on was provided by my interest in one particular aspect of the MHC and that was its polymorphism... its the remarkable property of the H2 and HLA system, of the existence of multiple alleles... different forms of the genes in the populations in appreciable frequencies, which is usually more than 1%. It is a striking feature of the MHC that it makes it rather unique because there are very few genes or perhaps it's the most polymorphic gene that exists at least in higher vertebrates.

So early in my interest in the H2 I started population studies of H2 in mice that were trapped in the wild. Most of the work, well, actually almost all the work that was done on MHC before was done on H2... was done on inbred strains of mice, but I wanted to expand it to see what the real polymorphism of the MHC is in the inbred strains... number of alleles or so-called haplotypes combinations of alleles were defined, but there was no study on mice caught in the wild. And so I started in Michigan by trapping mice, going to the farms and setting up traps. Every morning I would go and collect the mice that overnight were trapped in the different farms. You might think it's nothing easier than to catch a mouse, but in fact it's not that easy because you have to first find places where there are mice, you have to learn what is a sign of presence of mice in a barn or on a farm. Most farmers would claim they have no mice so it's... of course because it's... they consider it a bad thing to have mice in their barns, so they would not admit that there are mice. So you cannot ask the farmers, you have to find out for yourself. Eventually I did realize and my experience from my childhood helped me in that regard and so I located a number of farms where there was... that turned out to be very good trapping places. And then you have to have the right traps and you have to know where to put the traps and so on, you have to take care that the mice don't freeze in the traps because at night it gets cold and if it's a metal trap then it gets freezing cold in the trap so you had to provide some nesting material in which they could hide, and so on and so on.

Well, I was very successful in that part and every morning I was bringing back mice, which I decided to breed. Well, that also is easier said than done because while mice are proverbial in their reproductive ability, when you bring them from the wild their sexual urges somehow diminish. Not the males, the females have a problem and you have to set up a certain kind of condition for the mice that they... that the females feel like having sex, so that too I had to learn and eventually I was able to breed them.