Friday, October 15, 2004

Memory cells

Memory cells allow the body to remember previous infections and quickly mobilize defenses against them. This is the mechanism by which the human body remembers that someone contracted chicken pox, for example, and which prevents future infections of that type from occuring.

Time is short, so instead of discussing this at greater detail, I'll post a (slightly paraphrased, for brevity) excerpt from a technical paper on this subject.

Single-Cytokine-Producing CD4 Memory Cells Predominate in Type 1 and Type 2 Immunity

The patterns of Ag-induced cytokine coexpression in normal, in vivo-primed CD4 memory T cells has remained controversial because the low frequency at which these cells occur has effectively prevented direct ex vivo measurements. We have overcome this limitation by using two-color cytokine ELISPOT assays and computer-assisted image analysis. We found CD4 memory cells that simultaneously expressed IL-2, IL-3, IL-4, IL-5, and IFN--y to be rare (0-10%). This cytokine segregation was seen in adjuvant-induced type 1, type 2, and mixed immunity to OVA, in Leishmania infection regardless of the Ag dose used or how long after immunization the assay was performed. The data suggest that type 1 and type 2 immunity in vivo is not mediated by classic Thl or Th2 cells but by single-cytokine-producing memory cells.

Alexey Y. Karulin, Maike D. Hesse, Magdalena Tary-Lehmann, and Paul V. Lehmann, The Journal of Immunology, 2000, 164: 1862-1872.