Fig. 2.

Anti-CD68 reactivity in the anterior olfactory nucleus. A Example of immunohistochemical staining for CD68 in the human olfactory bulb [case #10]. Scale bars represent 100 µM. B Representative images of semi-quantitative scoring of staining, with scale from 0 to 5, in the AON. Scale bars represent 50 µM. C Average staining score for each diagnostic group; filled triangle in the OND group indicates a multisystem atrophy case. D Scatter plot showing correlation between age and CD68 score for all groups. Significance was determined using Kruskal–Wallis test with Dunn's post-hoc, where * indicates p ≤ 0.05 (C)

and Pearson's correlation where r = − 0.4494 (D). Straight line in D denotes correlation for COVID19 + cases. HCO denotes neurologically healthy controls; NCO, neurological controls; LBD, Lewy body diseases; AD, Alzheimer disease; OND, other neurodegenerative diseases