C1QA and Alzheimer disease: Notably, compared to the NC samples, the AD samples exhibited a smaller proportion of the m6 subpopulation, which expresses genes important for synaptic pruning (i.e., C1QA, C1QB, and C1QC, which encode complement component 1q) and cytokine response (i.e., IL4R and IL1RAP) (SI Appendix, Fig. S6 C and D).