Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Expansions are indicated with group identifiers and arrows. The tree is rooted at the branch separating Class I and Class II receptor clades. The Class I receptor clade is indicated with an open box.
