ACTH-dependent modulation of malaria immunity in mice

Area of Science:

• Immunology
• Endocrinology
• Infectious Diseases

Background:

• Malaria immunity is crucial for combating Plasmodium berghei infections.
• Corticosterone, a stress hormone, is known to modulate immune responses.
• Pregnancy is associated with a natural decrease in malaria immunity.

Purpose of the Study:

• To investigate the role of adrenocorticotrophic hormone (ACTH) and corticosterone in regulating malaria immunity.
• To determine if elevated corticosterone levels can induce loss of established malaria immunity.
• To explore the sensitivity of malaria immunity effector functions to corticoids.

Main Methods:

• Administered tetracosactrin, a synthetic ACTH analogue, via osmotic minipumps in mice.
• Measured plasma corticosterone levels following tetracosactrin treatment.
• Assessed malaria immunity in mice infected with Plasmodium berghei after treatment.
• Performed adrenalectomy and treated mice with dexamethasone to further probe corticoid effects.

Main Results:

• Tetracosactrin induced a dose-dependent increase in plasma corticosterone.
• Elevated corticosterone levels correlated with a loss of immunity against Plasmodium berghei.
• Adrenalectomy prevented both corticosterone increase and malaria immunity loss.
• Adrenalectomized mice lost malaria immunity when treated with dexamethasone, confirming corticoid sensitivity.

Conclusions:

• Elevated corticosterone levels, induced by synthetic ACTH, can lead to the loss of malaria immunity.
• The effector function of malaria immunity is sensitive to corticoids.
• Naturally occurring serum corticosterone levels, particularly during pregnancy, may regulate malaria immunity.