Conversely, activated and secreting CD4 regulatory T cell %CD4+ T cell (OR = 0.847, 95% CI = 0.722–0.993, P = .041), CD4-CD8- Natural Killer T %T cell (OR = 0.545, 95% CI = 0.323–0.920, P = .023), CD4-CD8- Natural Killer T %lymphocyte (OR = 0.533, 95% CI = 0.310–0.917, P = .023), natural killer %CD3- lymphocyte (OR = 0.638, 95% CI = 0.416–0.980, P = .039), IgD on IgD+ CD24+ B cell (OR = 0.714, 95% CI = 0.513–0.995, P = .047), and IgD on transitional B cell (OR = 0.699, 95% CI = 0.496–0.985, P = .041) were identified as protective factors for SCLC. Here, CD24 is linked to small cell lung carcinoma.