The major protein constituent of Lewy bodies (LBs), the pathological hallmark of 
Parkinson disease and dementia with Lewy bodies, is considered to be 
alpha-synuclein, but other proteins, in particular the microtubule-associated 
protein tau, have been implicated in the pathogenesis of LBs. Tau is the major 
structural component of neurofibrillary tangles (NFTs). Both direct 
immunochemical studies of partially purified LBs and indirect 
immunohistochemical studies have suggested that LBs may contain tau, but most of 
these studies were based upon a single tau antibody, and immunologic 
cross-reactivity was not completely excluded. To gain insight into the relation 
between tau and alpha-synuclein in LBs, double immunostaining was performed in 
Lewy body cases with a rabbit polyclonal antibody to alpha-synuclein and a panel 
of monoclonal antibodies to phospho- and nonphospho-tau epitopes (Alz50, CP9, 
CP13, PG5, TG3, PHFI) that spanned the length of the tau molecule. 
Tau-immunoreactive LBs were present in the medulla in 80% of the cases, 
irrespective of Braak stage. All tau antibodies recognized at least some LBs, 
arguing against nonspecific antibody cross-reactivity. In most lesions the tau 
immunostaining was present at the periphery of the LB. The phospho-tau antibody, 
TG3, detected more LBs than any of the other tau antibodies. The proportion of 
LBs with tau immunoreactivity was greatest in neurons vulnerable to NETs, such 
as those in the locus ceruleus and basal nucleus of Meynert, and least in 
neurons resistant to NFTs, such as the dorsal motor nucleus of the vagus in the 
medulla. The present results suggest that tau may coaggregate with 
alpha-synuclein in LBs, especially in neuronal populations vulnerable to both 
NFTs and LBs.