Myasthenia gravis lambert eaton myasthenic syndrome

Which of the following statements regarding myasthenia gravis is true?

1: Myasthenia gravis is an autoimmune disease
2: Myasthenia gravis is an example of a type 3 hypersensitivity reaction
3: Myasthenia gravis is associated with HLA-DR4
4: Myasthenia gravis only affects elderly patients