Lactation modifies stress-induced immune changes in laboratory rats

Area of Science:

• Immunology
• Neuroendocrinology
• Stress Physiology

Background:

• Both lactation and stress significantly impact immune system activity.
• The combined effects of lactation and stress on immune defense mechanisms are not well understood.
• Investigating these interactions is crucial for understanding maternal health and stress resilience.

Purpose of the Study:

• To examine the impact of acute social stress on cellular immunity in lactating and non-lactating rats.
• To compare immune responses in blood and mesenteric lymph nodes (MLN) under stress during lactation.
• To identify how lactation modifies the immune system's reaction to social stress.

Main Methods:

• Utilizing a social confrontation model to induce acute social stress (2 hours) in Long-Evans rats.
• Measuring plasma corticosterone concentrations to confirm stress induction.
• Assessing cellular immunity parameters, including granulocytosis, lymphocyte proliferation, cytokine production, phagocytosis, and immune cell populations (B cells, monocytes) in blood and MLN.

Main Results:

• Acute social stress increased corticosterone, caused granulocytosis, and reduced lymphocyte proliferation and cytokine production in the blood of both lactating and non-lactating rats.
• Lactation alone altered immune parameters, including increased granulocytes, enhanced phagocytosis, decreased B cells, and reduced IL-2 in blood.
• In MLN, lactation increased lymphocyte proliferation and monocyte numbers, while stress had no significant effect.
• Notably, stress-induced increases in blood granulocytes and decreases in IL-2 were only observed in non-lactating rats, indicating lactation-specific immune modulation.

Conclusions:

• Lactation significantly alters immune cell profiles and responses in both blood and MLN.
• The neuroendocrine state during lactation appears to buffer or impede certain stress-induced immune changes.
• These findings highlight a unique immune regulation during lactation that influences stressor impact on immune parameters.