'Hygienic' lymphocytes convey increased cancer risk

Area of Science:

• Immunology
• Microbiology
• Cancer Biology

Background:

• Industrialized nations show rising inflammation-associated cancer rates.
• Societal factors like antibiotic use and C-sections may limit early microbial exposure.
• The 'hygiene hypothesis' suggests microbial exposure shapes immune responses.

Purpose of the Study:

• To investigate the impact of limited early microbial exposure on immune cells and cancer development.
• To determine if CD4+ lymphocytes, influenced by microbial exposure, affect inflammation-associated cancer growth.

Main Methods:

• Utilized an adoptive cell transfer model in mice.
• Collected CD4+ lymphocytes from donors with restricted or normal microbial exposure.
• Transferred lymphocytes into recipient mice genetically susceptible to intestinal tumors (Apc mice).

Main Results:

• CD4+ lymphocytes from 'restricted flora' donors increased tumor multiplicity and malignancy in recipient mice.
• Observed heightened inflammatory cell infiltration and intestinal microbiota instability.
• Limited microbial exposure led to exacerbated inflammation-associated tumorigenesis.

Conclusions:

• While CD4+ lymphocytes normally maintain homeostasis, under conditions of limited microbial exposure, they can promote cancer.
• Insufficient early microbial exposure contributes to increased inflammation-associated cancer risk in industrialized societies.