I never had knowledge of one. there are a lot of clinics that practice hair implantation for androgenic alopecia. I never heard about any rejection., but most of that stuff happen commercially

There are talks on Androgen receptor gene on Chromosome 20. It may increase the risk by 7 folds, I do not think will be a definitive test.

There is some genetic testing of AR being done, but mostly in relationship to the diseases it is associated with. Please see this link and you will understand what I mean.   http://www.ncbi.nlm.nih.gov/gtr/tests/?term=367%5Bgeneid%5D

Androgenic alopecia without disease is caused by a number of genetic and environmental factors.  As Mohamed stated there are variations in only one gene, AR, which have been confirmed in scientific studies. The AR gene provides instructions for making a protein called an androgen receptor. Androgen receptors allow the body to respond appropriately to dihydrotestosterone and other androgens. Studies suggest that variations in theAR gene lead to increased activity of androgen receptors in hair follicles. It remains unclear, however, how these genetic changes increase the risk of hair loss in men and women withandrogenetic alopecia. In one region of the AR gene, a DNA segment known as CAG is repeated multiple times. This CAG segment is called a triplet or trinucleotide repeat. In most people, the number of CAG repeats in the AR gene ranges from fewer than 10 to about 36. The resource I used for this answer is the following, and very helpul in answering your question:  https://ghr.nlm.nih.gov/gene/AR#resources

They are only testing for the AR gene is diseases linked with the androgen receptor such as hypospadias, androgen resistance and spinal and bulbar muscular dystrophy. 

Hope that helps,

Diane