Protection against disseminated disease following reinfection with Mycobacterium tuberculosis requires CD8+ lymphocytes

Depleting CD8-expressing cells in non-human primates during secondary Mycobacterium tuberculosis challenge fails to limit dissemination, showing significant lymph node involvement after a short 4-week infection.

• Why it matters: Concomitant immunity is protective after prior TB exposure, but the specific contribution of CD8+ lymphocytes—beyond CD4 T cells—was unclear.
• What they did: In an NHP model of secondary Mtb exposure, investigators depleted CD8-expressing cells and assessed whether CD4+ airway T cells could compensate, then measured dissemination and lymph node involvement after 4 weeks.
• The result: CD8 depletion reveals a non-redundant requirement for CD8+ lymphocytes in controlling Mtb spread, implying vaccines should elicit both CD4+ and CD8+ responses for maximal efficacy.

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