Generally, a haplotype is a series of known DNA sequences or "markers"
that are inherited together on the same chromosome. When 2 people have a
similar haplotype, there is a greater likelihood of a familial relationship.
HLA (Human Lymphocyte Antigen) complex refers to a family of more than 200
genes linked closely together on chromosome #6, whose job is to encode
proteins necessary for the body's immune response and fight against disease.
HLA testing is often used for matching tissue types for bone marrow and
The HLA classes consist of several genes with many different variants and
an individual is classified by his overall HLA "type." The closer the
HLA type match between 2 individuals, the higher the probability of sharing
a common and more recent ancestor.
As a side point, we are learning more and more about HLA genes and disease
associations. Testing allows for the assessment of disease risks and
development of tailored treatments.
With regard to your specific question, I'm not familiar with HLA testing
being specifically used for genealogy purposes. Perhaps someone else will
be able to shed light on whether that is done on a routine basis. My
interest and experience has more to do with the disease associations, but the
concept of sharing a common ancestor rings true with two people sharing a
similar HLA type. However, I would imagine that in order to use this purely
for genealogy purposes, there needs to be a bank of sorts, with which to
identify similar HLA types.
Best of luck