Cutting edge: migration to nonlymphoid tissues results in functional conversion of central to effector memory CD8 T cells

Abstract

Memory CD8 T cells, essential for defense against intracellular pathogens, are heterogeneous with respect to phenotype and function. Constitutively lytic effector memory cells primarily reside in nonlymphoid tissues, whereas secondary lymphoid tissues contain functionally quiescent central memory cells. However, the mechanism by which functionally distinct memory populations are maintained is unknown. In this study, we show that resting CD8 memory cells modified their functional abilities upon entry into nonlymphoid tissues, as exemplified by the induction of granzyme B and lytic activity. Contemporaneously, the costimulator CD27 was down-regulated. These findings hold important implications for memory cell lineage development and tissue-specific immunity.

FIGURE 1

Phenotype and granzyme B expression of splenic and nonlymphoid memory CD8 T cells. 1 × 10³ CD45.1 OT-I-RAG^−/− splenocytes were transferred into CD45.2 mice and 1 day later the mice were infected with 1 × 10³ cfu of LM-ova i.v. and 46 days post infection re-infected with 1 × 10⁶ pfu VSV-ova i.v. 70 days later the level of CD62L, CD27 and GrB expression of the OT-I memory CD8 T cells was measured by flow cytometry. Values indicate the mean fluorescent intensity (MFI) of staining for the population. For GrB staining the MFI is shown for the isotype control and test, respectively. Data are representative of 3–4 mice analyzed from two experiments.

FIGURE 2

Splenic CD8 T_CM down-regulate CD27 and acquire granzyme B after entry into nonlymphoid tissues. OT-I transferred CD45.2 mice were infected with 1 × 10³ CFU of LM-ova i.v. 48 days later mice were re-infected with 1 × 10⁶ PFU VSV-ova i.v., and 97 days later, splenocytes were isolated, enriched for CD8 T cells, donor cells were sorted into either CD62L^low/CD27^high cells (A) or CD62L^high/CD27^high cells (B) and transferred to naive CD45.2 mice (1×10⁶ and 5×10⁵, respectively). Four days later lymphocytes were isolated from the spleen, lung, and liver, and the level of CD27, CD62L, and granzyme B expression by the transferred OT-I T cells was determined. C, OT-I transferred mice were infected with LM-ova i.v.; 46 days later mice were infected with VSV-ova i.v., and 58 days later splenocytes were isolated, enriched for CD8 T cells, donor cells were sorted, and 8.5 × 10⁵ CD27^high cells were transferred to naive CD45.2 mice. On days 0, 1, and 2, mice were treated with either 250 µg of anti-CD70 (FR70) or control rat IgG. Four days later, lymphocytes were isolated from the spleen, lung and liver, and the level of CD27 was determined on the transferred OT-I T cells. Values indicate the MFI of staining for the population. For GrB staining the MFI is shown for the isotype control and test, respectively. Data are from one representative animal of 1–4 mice analyzed from four experiments (n = 9).

FIGURE 3

Splenic CD8 T_M acquire lytic activity after entry into nonlymphoid tissues. CD45.2 B6 mice were infected with 1 × 10⁵ PFU of VSV-Indiana, rested for 71 days and infected with 1 × 10⁵ VSV-New Jersey. Approximately 9 mo after the secondary infection, CD8 T cells were enriched from the spleens and transferred to CD45.1 B6 mice; 4 days posttransfer tetramer⁺ CD8 T cells were sorted from the spleen and lungs and set up in a CTL assay. Experiments were performed twice with similar results, and the data are the mean of three mice from one experiment.

FIGURE 4

Nonlymphoid T_EM cells modulate CD27 expression but retain granzyme B following transfer. OT-I transferred CD45.2 B6 mice were infected with LM-ova and 48 days later were infected with VSV-ova i.v.; 97 days later, CD62L^low liver memory T cells were sorted and 1 × 10⁵ OT-I cells were transferred to naive CD45.2 B6 recipients, and 4 days posttransfer CD27, CD62L, and granzyme B expression of OT-I cells from the spleen, lung, and liver was determined. Values indicate the MFI of staining for the population. For GrB staining, the MFI is shown for the isotype control and test, respectively. Data are from one representative animal of two mice analyzed from two experiments.