  Recently Maldacena, Moore, and Seiberg (MMS) have proposed a physical
interpretation of the Atiyah-Hirzebruch spectral sequence, which roughly
computes the K-homology groups that classify D-branes. We note that in IIB
string theory, this approach can be generalized to include NS charged objects
and conjecture an S-duality covariant, nonlinear extension of the spectral
sequence. We then compute the contribution of the MMS double-instanton
configuration to the derivation d_5. We conclude with an M-theoretic
generalization reminiscent of 11-dimensional E_8 gauge theory.
