Scientists recently uncovered a key finding that CD4 T cells are not involved with Multiple Sclerosis progression after recent trials revealed that a depleting CD4-specific antibody failed to affect MS. The question is: did the depleting CD4 specific antibody fail to affect MS, or was the experimental design flawed? Essentially, immunologists claim that CD4 cells are at the center of the immunological research world simply because they are involved with other aspects of immune responses in order to be able to do what they do.
Zastepa et al., (Neurology Jan. 2014) have looked at whether altered naïve CD4 T-cell biology contributes to development of disease progression in secondary progressive multiple sclerosis (SPMS). The researchers were able to compare naïve CD4 T-cell gene expression profiles of 19 patients with SPMS vs 14 healthy controls using a whole-genome microarray approach. They looked at surface protein expression of critical genes by flow cytometry after T-cell receptor (TCR) activation of naïve CD4 T cells isolated from healthy controls and patients with SPMS.
The researchers separated patients with SPMS into two subgroups: SP-1, which had a short duration of relapsing-remitting MS, and SP-2, which had a long duration of relapsing-remitting MS. They discovered that SP-1 patients upregulated many immune genes, within the TCR and toll-like receptor (TLR) signaling pathways. SP-2 patients demonstrated down regulation of immune genes in comparison with healthy controls. They also found an SP-1-specific transcriptional signature of 3 genes which includes TLR4, TLR2 and chemokine receptor 1. These genes had a higher surface protein expression in SP-1 than SP-2. After researchers stimulated TCR for 2 days, only SP-1 showed a progressive linear increase in TLR2 and TLR4 protein expression.
The researchers suggest that changes in naïve CD4-T-cell biology, particularly that of TCR and TLR signaling pathways, identify MS patients with a rapid conversion to secondary progression. This is important because this identifies long-term disability in MS. In fact, certain proteins are in higher concentration on T cells from progressive MS patients that progress faster. What are these proteins doing you ask? That is not known as this time, however Toll-like receptors involved with microbe recognition and infections are important to the rate of progression. We know that blocking CD4 activity doesn’t stop progression, but the question is whether it changes the slope (rate of change). We expect to find this answer from the SP1 and tysabri trials.