Appendix 1—figure 1. Steps for preparing a two-dimensional dilution series of LL37 and cells.

(A) 50 $\mu$l/well of a 1 $\mu$M solution of LL37 in the growth medium (RDM) was transferred to all of the wells excluding row A, columns 7 and 12. Next, 150 $\mu$l/well of a 2 $\mu$M solution was transferred to the wells of row A, leaving columns 7 and 12 blank. A 2/3-fold serial dilution was then carried out vertically on all rows, A through H. (B) 150 $\mu$l/well of a linear dilution series of LL37 was was transferred to columns 7 and 12, with highest concentrations located in row A, while the lowest in row H. The concentrations chosen were 6, 5.34, 4.67, 4, 3.33, 2.67, 2 and 1.33 $\mu$M. (C) A 2/3-fold serial dilution was carried out horizontally from Columns 12 through 8 and Columns 7 through 1. The final volume of the solution in each well was 100 $\mu$l. (D) A cell culture was diluted to a final OD₆₀₀ of 0.02 and 50 $\mu$l/well was transferred into the wells located in column 12. A 2/3-fold dilution series was performed in a separate reservoir and 50 $\mu$l/well was transferred to column 11. The process was repeated for columns 10, 9, and 8. (E) The cell culture diluted to the OD₆₀₀ = 0.016 (80% of the culture used for column 12). 50 $\mu$l/well was transferred into the wells located in column 7. For columns 6 through 1, the same volume was transferred to each well after repeating 2/3-fold dilutions of this culture. (F) The final concentration of LL37 and cell densities in the microplate.