  Self-generated gradients (SGG) provide robust steering cues that guide cells
in their long-distance expeditions during embryonic development, immune
response, and cancer metastasis. Cells generate their own local, dynamic
gradients by breaking down the broadly distributed attractants in the
environment, which leads to propulsion. How cells sense the environment and the
interplay of self-generated force and long-range range chemotactic interactions
determines the collective behavior of cells in vivo is largely unknown. We
develop a theory to provide quantitative insight into how self-generated
chemotaxis (SGC) steers the collective migration of cells during their
long-distance journeys. In an externally imposed gradient, the cells exhibit
super-diffusive motion at time less than persistent time ($\tau_p$) and exhibit
diffusive motion at time $t>\tau_p$. On the other hand breakdown of
chemo-attractants influences the density fluctuations and long-range
correlations emerge in the density of chemotactic cells. The cells exhibit
superdiffusive motion at a longtime limit. The SGG provides an effective
mechanism for long-distance travel compared to an externally imposed gradient.
Our theory provides a general framework for studying the non-equilibrium
dynamics of collections of interacting particles.
