CD4 and congenital primary aphakia: In addition, some patients with CPA are subtly immunocompromised, as has been documented with nonprotective pneumococcal or Haemophilus antibodies (52); low circulating CD4 (T helper), CD19 (B cell), or CD56 (natural killer) cell counts (53); and poor production of gamma interferon interleukin 17A, interleukin 12, or both (54).