Recognising it is not enough
if you never arrive
Most immunology is about recognition. But there is a problem before that โ the cell has to get there.
The tumours in this paper have plenty of mutations, intact antigen presentation, and no T cells. The paper writes: anti-PD1 alone recruits lymphocytes but does not drive them into the tumour core.
These twenty lessons teach that grammar and then score that claim against coordinates. With 100,000 cells you measure 'infiltration' five ways โ and the five disagree. Choosing a metric turns out to be choosing a conclusion.
How you'll learn
Chemokines set direction, selectins slow the cell down, and only past the chemokine checkpoint do integrins unfold. Block any one of seven steps and the T cell never arrives.
Count, fraction, density, distance, neighbourhood composition. Same data, five different answers โ the first three favour the combination, the last two favour the control.
In the combination, lymphocytes sit farther from tumour cells. Did they fail to enter โ or had they already cleared that area? Proliferating tumour cells fell 4,041 โ 502.
Split the paper's claim into three: two are supported, one is undecidable. The numbers point the other way, but the alternative explanation could not be ruled out.