Vampire Compatibility
Clip, 69

*cTx\{fFx`Tf[tFtx}T`[Fx[y!VVx"O-"Vy"O-"}[TC"A+ B+ AB+ O+ A- B- AB- O-


Input: AB-

Output: {{"AB+", "AB-"}, {"A-", "B-", "AB-", "O-"}}

Explanation

A blood type x can give to y if all of x's antigens are included in y. The program defines the function F as whether x can give to y, and T as the list of types.

*cTx                 .- If T contains x (the input)         -.
    \                .- Print                               -.
     {             ` .- a list of                           -.
      fFx`T          .- filter each t in T with F(x,t)      -.
           f[tFtx}T  .- filter each t in T with F(t,x)      -.

[Fx[y              } .- F is a function of x and y          -.
     !V              .- all letters of ... are included in ...   -.
       Vx"O-"        .- x, with O and - removed             -.
             Vy"O-"  .- y, with O and - removed             -. 

[TC"A+ B+ AB+ O+ A- B- AB- O-   .- T is the list of types -.