CD28 and asthma: The expression levels of CD27, CD28, CD59 and TCRab were higher, while CD38, CD39, CD45, CD45RO, RORγ and Tbet were lower in cluster 13 in acute pneumonia, stable pneumonia, acute asthma and stable asthma, while the levels of PD‐1 in pneumonia and acute asthma were higher, suggesting T cells of those patients may be more exhaustive.