We then proceeded in comparing the binding abilities of i-α1-ECD and y-α1-ECD to anti-nAChR autoantibodies present in five MG patients’ sera, using RIA experiments; three of these sera (sera #1, #2 and #3) have low to moderate titers of anti-nAChR autoantibodies (titers values of 1.9 nM, 16 nM and 15 nM, respectively) and two sera (sera #4, #5) have very high titers (1 and 2 μΜ, respectively). Here, CHRNA4 is linked to myasthenia gravis.