Anti-PD-1 (BMS-936558, MDX-1106) in patients with advanced solid Melanoma tumors: Clinical activity, safety, and a potential biomarker for response.Melanoma ..Jim Breitfeller

I have been following this new treatment for a number of years and am trying to get my arms around the science.

When a T-cell is activated, the PD-1 , CTLA-4, ICOS, and others molecule are expressed and upregulated to the surface of the T-cell. Both PD-1 and CTLA-4 are checkpoint molecules that regulate the immune response. They are inhibitory to the point that they can shut down T-cell activation. ICOS on the other hand is a costimulatory molecule that is needed, along with IL-2 to keep the T-cell activated and help proliferate the T-cells.Elevated levels of ICOS mRNA can be detected already one hour after TCR engagement, followed by surface expression within 12 hours. Protein expression reaches a maximum after 48 hours and declines then slightly.

It has been shown that ICOS is inducible within 48 hours of T  cell activation on both CD4+ and CD8+ cells  after  CD28 signaling  whereas cytotoxic T lymphocyte  antigen-4 (CTLA-4) ligation prevents its upregulation.

First, CTLA-4 engagement on resting T-cells was found to indirectly block ICOS costimulation by interferring with the signals needed to induce ICOS cell surface expression. Second, on preactivated cells that had high levels of ICOS expression, CTLA-4 ligation blocked the ICOS-mediated induction of IL-4, IL-10, and IL-13, suggesting an interference with downstream signaling pathways. The addition of IL-2 not only overcame both mechanisms, but also greatly augmented the level of cellular activation suggesting synergy between ICOS and IL-2 signaling.

So after T-cell Activation, IFN gamma is secreted (30 minutes), then IL-2 is secreted (45 minutes in) and so on,

The surface expression of ICOS is within 12 hours of activation. Since CTLA-4 blocks ICOS costimulation, Yervoy (anti-CTLA-4) must be used to counter the surpressive signalling. PD-1 also upregulates to the surface in the early activation process. PD-1 is upregulated within 24h after T cell activation.PD-1-Mediated Suppression of IL-2 Production Induces CD8+ T Cell ... anergy was associated with a marked down-regulation of IL-2.

Blockade of PD-1 by monoclonal antibodies specific to its ligands (PD-L1 and PD-L2) results in significant enhancement of proliferation and cytokine (gamma interferon [IFN-gamma] and interleukin-2 [IL-2] secretion by tumor-specific CTLs. PD-1 blockade also resulted in down-regulation of intracellular FoxP3 expression by Tregs.

PD-1 blockade seem to augment the proliferation of the CD4+ helper cells.

Now you know why just using Anti-PD1 and or Yervoy as a monotherapy will not have a large response rate. Combinational Therapy is a must if we are to see synergistic responses. IL-2 also plays a major roll in the immune response. IL-2 is added to help maintain fuctionality and survival of the Cytotoxic T Lymphocytes (CTLs) that is despartly needed to eradicate the Melanoma tumors. Our immune system can cure cancer, I am living proof of it.

Jimmy B



“It is not the strongest of the species that survives, nor the most intelligent, but the one most responsive to change.”
~Charles Darwin~
Take Care,
 Jimmy B