CD8 cells play a critical role in delayed type hypersensitivity to intact Cryptococcus neoformans

Area of Science:

• Immunology
• Microbiology
• Cellular Immunity

Background:

• Cell-mediated immunity is vital for host defense against Cryptococcus neoformans.
• The specific roles of T lymphocyte subsets, particularly CD8 cells, in this response are not fully understood.
• Delayed type hypersensitivity (DTH) is a key correlate of host defense against C. neoformans.

Purpose of the Study:

• To elucidate the mechanism by which CD8 cells participate in the DTH response to C. neoformans.
• To determine the necessity of CD8 cells during immunization, challenge, and effector phases of DTH.

Main Methods:

• Mice were immunized with live or heat-killed C. neoformans via intratracheal or subcutaneous routes, respectively.
• CD8 cells were depleted in vivo using monoclonal antibodies (mAb) before or after immunization.
• DTH response was assessed by footpad swelling after challenge with soluble cryptococcal antigen.
• Adoptive transfer experiments using splenocytes from CD8-depleted mice were performed.

Main Results:

• Mice depleted of CD8 cells before or after immunization failed to mount a DTH response.
• Splenocytes from CD8-depleted mice could not transfer DTH to naive recipients.
• CD8 cell depletion did not affect DTH responses to non-cryptococcal antigens (e.g., SRBC) mediated by CD4 cells.

Conclusions:

• CD8 cells are critically required for the induction, elicitation, and expression of DTH to C. neoformans.
• These findings suggest CD8 cells play a significant role in the cell-mediated immune response to C. neoformans.
• Targeting CD8 cell-stimulating immunotherapies may offer protection for individuals with CD4 cell deficiencies, such as in AIDS.