CD138 and CD31 Double-Positive Cells Comprise the Functional Antibody-Secreting Plasma Cell Compartment in Primate Bone Marrow

Abstract

Plasma cells (PCs) are defined as terminally differentiated B cells that secrete large amounts of immunoglobulin (Ig). PCs that reside in the bone marrow (BM) are responsible for maintaining long-term antibody (Ab) responses after infection and vaccination, while PCs present in the blood are generally short-lived. In rhesus macaques, a species frequently used for the evaluation of human vaccines, B cells resemble those found in humans. However, a detailed characterization of BM-resident rhesus PC phenotype and function is lacking. Here, we examined Ig secretion of distinct rhesus CD138+ populations by B cell ELISpot analysis to couple phenotype with function. We demonstrate that the CD20low/−CD138+CD31+ BM population was highly enriched for antibody-secreting cells with IgG being the predominant isotype (60%), followed by IgA (33%) and IgM (7%). Transmission electron microscopy analysis confirmed PC enrichment in the CD20low/−CD138+CD31+ population with cells containing nuclei with “spokes of a wheel” chromatin structure and prominent rough endoplasmic reticulum. This panel also stained human BM PCs and allowed a clear distinction between BM PCs and short-lived peripheral PCs, providing an improved strategy to isolate PCs from rhesus BM for further analysis.

Evolution of B cell analysis and Env trimer redesign

“…In nonhuman primates (NHPs), using the foldon trimers as immunogens, we defined a number of fundamental features of immune responses to Env vaccination, establishing a system amenable for high-resolution analysis of B cell responses following HIV trimer immunization. [36][37][38][39][40][41][42][43][44][45] We discuss the specifics of our high-resolution B cell studies in more detail below (Section 1.3).…”

“…In the cases where Ab cross-reactivity to macaque markers is insufficient or lacking, we have evaluated alternative markers, such as in our recent study of rhesus macaque bone marrow plasma cells. 45 A number of years ago, we developed strategies to clone antigenspecific MAbs from immunized rhesus macaques, adapted from B cell analysis of HIV-infected humans. 70 To achieve this objective, we developed antibody staining panels for flow cytometry-based cell sorting of macaque B cells and optimized primers for efficient isolation of macaque Ab transcripts from single cells.…”

“…However, despite the inability of these earlier trimer designs to fully mimic properties of the native spike, we learned a great deal by studying the B cell and antibody responses they elicit in the context of immunization, establishing analytical tools that are broadly used in the field today. In non-human primates (NHPs), using the foldon trimers as immunogens, we defined a number of fundamental features of immune responses to Env vaccination, establishing a system amenable for high-resolution analysis of B cell responses following HIV trimer immunization (37-46). We discuss the specifics of our high-resolution B cell studies in more detail below (Section 3).…”

“…Conveniently, the NIH Nonhuman Primate Reagent Resource summarizes the properties of an increasing number of cross-reactive MAbs to facilitate work in the NHP model. In the cases where Ab cross-reactivity to macaque markers is insufficient or lacking, we have evaluated alternative markers, such as in our recent study of rhesus macaque bone marrow plasma cells (46). …”

Cell Detection by Functional Inverse Diffusion and Non-negative Group Sparsity—Part I: Modeling and Inverse Problems

“…Localization enables counting, and therefore, quantitative studies of the proportions of active cells within the cell population under study. Thereby, these assays provide answers to relevant questions in fields ranging from biochemical, pharmacological, and medical research [5], [9], [10], to the diagnosis of specific diseases [11], [12]. Hence, source localization (SL) algorithms are critical to the development of automated analysis systems for high-throughput pharmacological and medical applications.…”