Let $\Psi_\Lambda^{\{\mu\}}\propto U_\Lambda^{\{\mu\}}$ and $\psi_\lambda^{\{\nu\}}\propto u_\lambda^{\{\nu\}}$ be spinors of spin $s$ fermions where $s \geq 1/2$ with respective helicites $\Lambda$ and $\lambda$ and indices $\{\mu\} = \{\mu_1,\ldots,\mu_n\}$, $\{\nu\} = \{\nu_1,\ldots,\nu_n\}$.
Given an invariant matrix element
$\mathcal{M}_{\Lambda\lambda} = U_\Lambda^{\{\mu\}} T_{\{\mu\}\{\nu\}} u_\lambda^{\{\nu\}}$
where $T_{\{\mu\}\{\nu\}}$ can be any kind of interaction, are there any symmetries concerning the helicities?
I'm suspecting it could be
$\mathcal{M}_{\Lambda\lambda} = \mathcal{M}^*_{-\Lambda-\lambda}$
and
$\mathcal{M}_{-\Lambda\lambda} = -\mathcal{M}^*_{\Lambda-\lambda}$
but I'm looking for proof or a reference about it.
