Multiphoton Exchange Amplitudes at Infinite Energy

We illustrate in detail the summation of multiphoton exchange diagrams for $\mathrm{ee}$, $\gamma e$, and $\gamma \gamma$ elastic scattering amplitudes at the high-energy limit using the infinite-momentum technique reported earlier. These diagrams are shown to give rise to amplitudes proportional to $s$, the center-of-mass energy squared, multiplied by simple combinations of the eikonal forms of high-energy scattering.