** Reference: The Cells of the Lungs, Sergei P. Sorokin,
Department of Anatomy, Harvard Medical School, Boston, Massachusetts.
(See below for complete reference)
PREFACE:
Are there really over 40 cell types in the lung? This statement is
found without a reference in many published manuscripts. It was first
published in 1970, 33 years ago, from the proceedings of a conference on
the morphology of experimental respiratory carcinogenesis. ** Today, it
is assumed that there are a myriad of different cell types in the lung.
Yet most investigators no longer study what the cells of the lung look
like. This is taken for granted in spite of a new cell being described
in 1990 (ref ATS in newsletter). Lung cell biologists, inhalation
toxicologists and other specialists study what the lung cells do, what
they contain, what mDNA codes for etc.
In this issue of the inhalation.net newsletter, an experienced
pulmonary cell biologist (Michael J. Evans, PhD, professor of anatomy at
UC Davis) and colleague of the Dr. Sergei Sorokin, author of the
statement reassesses the validity of the statement, "Well over 40
distinctive cell types make up pulmonary tissues" published by
Sorokin of Harvard Medical School in 1970.
ABSTRACT:
In 1970, Dr. Sergei Sorokin published the classic paper describing
cells found in the lung. He stated "Well over 40 distinctive cell types
make up pulmonary tissues. Most of these occur as well in other tissues
of the body, but a few are unique to the lungs". Forty four cell types
were actually described by Sorokin when one counts the numbers found in
his review. Seventeen of these cells were epithelial, 9 were in the
connective tissue, 7 were in blood vessels, and 5 were nervous tissue.
He described 2 types of bone cells, 2 types of muscle cells, one pleural
cell and one cartilage cell.
Sorokin’s description of the cells making up the lung is still
correct today with few exceptions. Of the 17 epithelial cell types he
identified 5 as not being present in all species. Removing these from
the list leaves 12 epithelial cell types.
Of the 9 cell types found in connective tissue, 7 are currently
classified as trafficking leukocytes and not considered to be part of
the lung structure. Removing trafficking leukocytes from the list leaves
6 blood vessel cells, 4 cells in nervous tissue, 1 type of muscle cell,
1 type of cartilage cell and 1 type of pleural cell.
This revised list leaves a total of 27 cell types that make up the
lung structure. Of these cells, Sorokin considered only 4 to be unique
to the lung: non ciliated bronchiolar cells or Clara Cells, squamous
cells (Type 1 cells), great alveolar cells (Type 2 cells) and alveolar
macrophages.
These 27 cell types are currently listed in textbooks as making up
the normal cell populations of the lung.
At the end of the formal talk is a prophetic statement made by
Sorokin: "My intention had been to stress that from larynx to alveoli,
cells in the pulmonary epithelium share many basic characteristics.
Please be patient while this
article is finished. We have published this much because we have
had numerous requests for it as the original reference is difficult to
find. (SgS)
** Reference: The Cells of the Lungs, Sergei P. Sorokin, Department
of Anatomy, Harvard Medical School, Boston, Massachusetts. In the
"Morphology of Experimental Respriatory Carcinogenesis". Pages 3 through
43 with 30 electron micrographs. Proceedings of a Biology Division, Oak
Ridge National Laboratory conference held in Gatlinburg, TN, May 13-16,
1970. Editors: P. Nettesheim, M.G. Hanna, Jr., and J.W. Deatherage, Jr.,
ORNL. Available from National Technical Information Service. Library of
Congress Catalog Card Number 73-609398.
