Question: MGS2 plot question

[Agent]

Hello, i've been playing MGS2 recently and I noticed soon after Raiden's entry into the big shell, he meets a Navy SEAL (lieutenant junior grade) called Iroquois Pliskin. However after the introduction this character never appears again, for the rest of the series as far as I know. Is it to be assumed he was killed on the big shell? Is he an important character in the story? I want to make sure I have it all straight as i'm sure part 4 will wrap things up in an intelligent way. Thanks!