I am not sure if I am the only one, but I found it surprising that the immune system components you mention (serum antibodies and upper respiratory tract mucosa

I am not sure if I am the only one, but I found it surprising that the immune system components you mention (serum antibodies and upper respiratory tract mucosal membrane) do not “learn from each other”. I suppose I had a naive / uneducated perspective on this, but is there an obvious reason why they don’t learn from each other?