But here we form a much larger peak concentration of antibodies. So peak simply means the highest value of these particular hills. Now, notice that during our decline phase we dropped to very low undetectable value in the primary case. But in the secondary case we dropped to a higher value. And because we have a higher value of antibodies during our decline phase, the secondary immune response will be much more efficient in actually binding the antibodies onto our antigens and destroying those antigens. And finally, we see that in the primary response we use immunoglobulin M. But in the second response we use immunoglobulin gene.