In this paper we are concerned with the regularity of solutions to a nonlinear elliptic system of $m$ equations in divergence form, satisfying $p$ growth from below and $q$ growth from above, with $p leq q$; this case is known as $p, q$-growth conditions. Well known counterexamples, even in the simpler case $p=q$, show that solutions to systems may be singular; so, it is necessary to add suitable structure conditions on the system that force solutions to be regular. Here we obtain local boundedness of solutions under a componentwise coercivity condition. Our result is obtained by proving that each component $u^alpha$ of the solution $u=(u^1,...,u^m)$ satisfies an improved Caccioppolis inequality and we get the boundedness of $u^{alpha}$ by applying De Giorgis iteration method, provided the two exponents $p$ and $q$ are not too far apart. Let us remark that, in dimension $n=3$ and when $p=q$, our result works for $frac{3}{2} < p < 3$, thus it complements the one of Bjorn whose technique allowed her to deal with $p leq 2$ only. In the final section, we provide applications of our result.
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