We discuss string spectra in the low-tension limit using the BRST formalism, with emphasis on the role of triplets of totally symmetric tensors and spinor-tensors and their generalizations to cases with mixed symmetry and to (A)dS backgrounds. We also present simple compensator forms of the field equations for individual higher-spin gauge fields that display the unconstrained gauge symmetry of a previous non-local construction and reduce upon partial gauge fixing to the (Fang-)Fronsdal equations.For Bose fields we also show how a local Lagrangian formulation with unconstrained gauge symmetry is determined by a previous BRST construction.

We construct the Lagrangian description of arbitrary integer higher spin massless fields on the background of the D -dimensional anti -de Sitter space. The operator constraints in auxiliary Fock space corresponding to subsidiary conditions for irreducible unitary massless representations of the D -dimensional anti -de Sitter group are formulated. Unlike flat space, the algebra of the constraints turns out to be nonlinear and analogous to the W 3 algebra. We construct the nilpotent BRST charge for this nonlinear algebra and derive on its basis the correct field content and gauge invariant action describing the consistent arbitrary integer spin field dynamics in AdS

We give a detailed review of the construction of gauge invariant Lagrangians for free and interacting higher spin fields using the BRST approach developed over the past few years.'Extended version of the contribution to the volume dedicated to the 60th-birthday of Prof I.L. Buchbinder'

We construct an off-shell extension of cubic interaction vertices between massless bosonic Higher Spin fields on a flat background which can be obtained from perturbative bosonic string theory. We demonstrate how to construct higher quartic interaction vertices using a simple particular example. We examine whether BCFW recursion relations for interacting Higher Spin theories are applicable. We argue that for several interesting examples such relations should exist, but consistency of the theories might require that we supplement Higher Spin field theories with extended and possibly non-local objects. *