Biology Reference
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F i g u r e 19.3. (A) HIV-1-induced T-cell depletion. Hu-PBL-SCID mice were challenged with
HIV-1 (either IIIB or SF-162 strain) at 2 h or 2 wks after engraftment and sacri®ced 4 wks later.
(B) E¨ect of HIV-1 infection on human IgM serum levels. Note that the levels of human IgM
directly correlate with the levels of human CD4 T cells.
in CXCR4 expression. The latter phenomenon can explain, at least in part, the
reduced susceptibility of hu-PBL-SCID mice to X4 viruses when injected at this
time. Notably, in vivo±induced alterations of the human T-cell phenotype are
not a unique characteristic of primary T cells. In fact, we had shown that sub-
cutaneously injected CEM cells acquire a memory-like phenotype, up-regulating
CD45RO, CCR2, CCR3, and CCR5, whose expression is associated with a high
susceptibility to the in vivo infection with the HIV-1 monocytotropic strain
SF162 and with a series of monocytotropic clinical isolates, which cannot infect
CEM cells in vitro (Lapenta et al., 1998). The susceptibility of CEM cells
transplanted into SCID mice to HIV infection is selectively inhibited by the b-
chemokines such as RANTES, macrophage in¯ammatory protein (MIP)-1a
and MIP-1b (the natural CCR5 ligands), and is progressively lost upon long-
term culture after explantation from xenochimeras. These ®ndings were highly
