Anti-GQ1b antibodies are autoantibodies that target the GQ1b ganglioside, a component of nerve cell membranes, and are strongly associated with certain autoimmune neurological disorders, particularly Miller Fisher syndrome (MFS) and Bickerstaff brainstem encephalitis (BBE). Their presence is a key diagnostic marker for these conditions, highlighting the role of molecular mimicry in autoimmune diseases where the immune system mistakenly attacks the body's own tissues.