Serial study of lymph node cell subsets using fine needle aspiration in pigtail macaques

Area of Science:

• Immunology
• Virology
• Pathogenesis Research

Background:

• Lymphoid tissues are crucial for understanding human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) pathogenesis.
• Non-invasive sampling of lymphoid tissues for longitudinal studies remains challenging.
• Fine needle aspiration (FNA) is a conventional diagnostic tool for lymphadenopathy.

Purpose of the Study:

• To evaluate the utility of serial lymph node (LN) fine needle aspiration (FNA) in pigtail macaques for studying immune cell subsets.
• To compare immune cell composition and functionality in FNA samples with whole excised LNs and peripheral blood.
• To assess the feasibility of using FNA for longitudinal research on SIV/HIV infection immunopathogenesis.

Main Methods:

• Serial LN FNA sampling was performed on pigtail macaques.
• Immune cell subsets (absolute count, frequency, functionality) were analyzed using flow cytometry.
• In vitro functionality was assessed via polyclonal SEB stimulation.

Main Results:

• FNA yielded sufficient lymphocytes (median 2.01×10^5) and CD4+ T cells (median 5.94×10^4) for analysis.
• FNA cell subset composition, particularly T cells and CD4+ T cells, was comparable to excised LNs and distinct from peripheral blood.
• T follicular helper (TFH) cells were identifiable in LN FNAs and correlated with B cell frequencies; in vitro functionality was comparable to circulating lymphocytes.

Conclusions:

• Serial LN FNA in macaques is a viable method for studying immune cell dynamics during SIV infection.
• This technique facilitates longitudinal research into SIV/HIV immunopathogenesis.
• FNA provides a valuable, less invasive approach compared to excising entire lymph nodes.